3d scanning modeling. 3D scanning methods
There are a great many virtual objects that can be printed using 3D printing on the Internet. So, without much difficulty you can find images of magnificent jewelry that will honor any fashionista, three-dimensional drawings of parts for intricate mechanisms and souvenirs with meaning. If desired, it will not be difficult to find even bulky models of shoes and clothing.
Not finding what you want in open access, you shouldn’t despair at all and give up the desire to have the best. If you have a good 3D printer at hand, capable of printing not only elephant figurines and bricks, but objects of more complex shapes, you can make your wish come true.
To do this, you will need a special scanner capable of reading three-dimensional information and storing it in the printer’s memory. 3D scanning is a task that even an ordinary school student can cope with. You just need to select the object you want to copy, for example, a model of a helicopter, and start reading...
Of course, such equipment costs a lot, but it eliminates the need to purchase expensive program to virtually build a model and master it.
Our company provides 3D scanning services, the prices of which are affordable. Almost complete identity of the original and the copy, reasonable price and minimal time investment - this can surprise you!
3D scanning services: we guarantee quality
As the demand for 3D printing has grown, so has the number of offers to fulfill such orders. But in order to put into shape an object depicted in three-dimensional format, it is necessary to have a sufficiently functional unit and good quality consumables.
If you have a printer, you can even “grow” a simple or complete model yourself - without anyone’s help. It’s another matter if you need to copy an object for which there is no 3D software model, for example, a scarce car part or a human leg joint. In such a situation, our company can help by providing 3D scanning services.
By using portable device, scanning objects in three-dimensional format, you can create their virtual models, and then manufacture them using casting or any other method. The price for 3D scanning services depends on the size of the object, as well as the characteristics of its surface. The more small parts there are, the higher the cost of such work will be, but will still remain quite affordable.
And this topic interested me very much, although I quickly realized that $30 for a high-quality scan was out of the question.
But the main advantage that I took away from the article is the David-3D scanning program, which actually has good guide in Russian and, importantly, purchasing a license is the last thing required, since the limitation is free version only to save the scan result. Everything else works fully, which means you can test the program, settings and your hardware as much as you like. And if you don’t need the result with high accuracy, then you can do without purchasing a license at all.
I needed accuracy, since the main thing I wanted to scan were miniatures from board game Warhammer (so that you can then change them as you want and print them :)). The height of these “soldiers” is only 3 cm, but this does not prevent them from being very detailed.
If you don’t need to shoot such small objects, then your equipment requirements will be lower, which means it will be much easier to assemble a similar scanner.
The principle of operation of the program, and accordingly scanning, is well described in the article linked above (I think it is not necessary to duplicate this). It is advisable to read that article first, since this one will in some way be its logical continuation.
But let's start in order. What you will need to try 3D scanning at home:
1 – projector.
2 – web camera.
That's all, the short list turned out surprisingly well. However, if you want to get very accurate and high-quality scans, you will have to do some manual modifications. Of course, this cannot be done without additional costs, but in the end it will still cost less than buying any of the commercially available 3D scanners, and the quality of the result can be obtained much better.
Now in order and in detail.
PROJECTOR.
I, like the author of the previous article, started my first scanning experiments with a laser pointer, but they immediately showed how inconvenient this method was. There are several disadvantages here:
– impossibility of obtaining a beam with a sufficiently thin line. Moreover, when you turn the pointer, the distance from the lens to the object changes, which means the focusing is lost.
– if you need to scan regularly, rotate laser pointer with sufficient accuracy and smoothness manually it is very difficult, and even tiring - hands are not such a stable tool when we're talking about about a long time.
– you have to scan in the dark so that only the laser line is visible and nothing more.
And if the second drawback can still be dealt with by creating a special rotating mechanism (although this is no longer so simple task, in any case, you can’t do this in 5 minutes on your knee), then getting rid of the first drawback is more expensive.
When I realized all this, I decided to try scanning using a projector, for which I borrowed some simple model at a friend's place.
A small clarification should be made here - in the last article the author mentioned the possibility of scanning using a projector, although the proposal was, in my opinion, very strange -
A projector with a powerful lamp is suitable, the light of which must be directed through a narrow slit onto the object being scanned
Perhaps in earlier versions of the program this was the only option, but in version 3, which I experimented with, the projector was used much better, because... there is a feature called Structured Light Scanning (SLS). Unlike laser scanning, the projector immediately projects a grid of vertical and horizontal lines of varying thickness onto the object, which reduces scanning time by an order of magnitude and allows automatic mode shoot the color texture of an object. Well, with good focusing, a line 1 pixel wide is much thinner than what can be obtained from an inexpensive laser pointer.
Unfortunately, I didn’t take any photographs from those first experiments, and there wasn’t much to photograph - there was a projector on the table, a webcam next to it, it all looked in one direction :) However, even this simplest design showed that this option is much preferable both in terms of scanning speed and quality. Then I decided to buy myself a projector for these purposes.
The criteria for choosing a projector were simple - higher resolution, smaller price and size :)
The choice settled on IconBit Tbright x100 - ultra-compact DLP LED projector, resolution 1080 - at that time it seemed to me that you couldn’t imagine anything better, but as it turned out later, I was wrong, although working with it, I got a lot of interesting experience.
The first problem that arises when scanning a small object with a projector is that for best results, the size of the projected grid should approximately match the size of the object being scanned. This projector made it possible to obtain the smallest screen diagonal at the closest focus - approximately 22 cm. You will agree that against such a background, a miniature 3 cm high is far from the concept of “approximately equal dimensions.” The answer was found on the official forum - in such cases, people install camera lenses on the projector for macro photography. Considering the small size of the projector lens, I opted for marumi lenses with a thread diameter of 34 mm.
Using two such kits, we managed to get a projector screen with a diagonal of only about 3 cm. Which turned out to be quite enough to make my first microscan - 
This is a single scan, which is why there are “holes” in the model, torn edges, etc. By rotating the coin and scanning from different angles, you can get several such scans, which are subsequently combined into one object (the scanning program itself allows you to correctly combine different scans, stitch them together and save them as a single object). During the stitching process, the shape of the object is also refined. But saving the results of such stitching is possible only after purchasing a license.
And now the time has come for the first thing that is not required for scanning, but with it the process is much more convenient - this is a stand for a projector with a camera. The calibration process itself is needed not only for the program to recognize the equipment parameters - the software must also calculate mutual arrangement camera and projector. During the work, changing them is not allowed (as well as changing the camera focus), which means that it all needs to be firmly fixed, because the number of scans can be large even for one object.
On David's main page a similar system is depicted - it is not anything complicated. And after looking through the forum and seeing how different people organize it for themselves, I realized that nothing complicated is required here.
For these purposes, we took a stand from a burnt LCD monitor, and plexiglass from it, cut out and glued together this design, as it looked in the first version
A mount for installing various lenses was attached to the projector stand, which made it possible to change the diagonal of the screen and scan objects of different sizes.
It should also be mentioned that scanning using a projector does not require the calibration panels to be constantly in view. After calibration is completed, they can be removed. This allows you to calibrate the installation, easily carry it, move it, etc.
That is, you can use a large calibration template to perform calibration on the walls at home, and then with this stand and laptop go outside and scan your car, for example. We took a smaller template, added a couple of lenses, and we were ready to scan jewelry.
Recently the company released an improved scanning kit, now the stand is much more serious and looks more interesting -
As for me, given the cost of a license for the program is about $500 (they raised the price recently), paying more than 2000 euros for such a set is not entirely justified; it’s not difficult to assemble something like this yourself and is much cheaper.
Let's return to the projector. As it turned out, this projector had one significant drawback for use in a scanner, namely its native resolution(854*480). And everything would be fine if it produced the same thing at the output, but alas - the picture was converted to standard resolutions (such as 1024 * 768), and as a result, a line one pixel wide was somewhere brighter in different parts of the screen, where -sometimes dimmer, sometimes narrower, sometimes wider... All this had a negative impact on the quality of the scan, manifesting itself in the form of ripples and stripes on the resulting model.
By that time, I was already thinking about buying a projector for a stereolithographic 3D printer (). After considering several options, I settled on the Acer P1500 model, because... it does not need any modifications to be used in a printer (this projector, without any lenses, is capable of producing a focused image on a screen of approximately 4*7 cm). This means that it is perfect for a scanner. Moreover, it has a real resolution of 1920*1080. And so it happened, I still use this projector and am completely satisfied with the results.
CAMERA.
My criteria for choosing a camera were the same as when choosing a projector. After shopping, I settled on the Logitech C615. The scan of the coin was made exactly from it, without any modifications. But when I tried to scan the figure, I ran into a problem called “depth of field.” When the object is so small, then in fact we get macro photography, and sharpness during such shooting is achieved only in a small segment, literally just a couple of millimeters (this is why the coin was scanned well - the relief fit well into the sharpness area). It was decided to remake the camera for a different lens. Several different lenses were ordered from Ebay for testing, and a new housing was cut out for the camera board. The plan was like this
The final result was slightly different
The main idea, I think, is clear. And now on Thingiverse and on the program forum you can download stl for printing enclosures for different types webcams.
The standard lens had to be removed from the camera board, and as it turned out later, the IR filter was also removed along with it, so be careful in this matter. The filter will then be useful for use with other lenses, although you can buy them separately - the price is a pittance.
Thus, I have this collection of lenses.
While I was waiting for the lenses to arrive, I was reading various photography forums. While studying the issue of depth of field, I found out that it can be increased by closing the lens aperture further. This means that a lens was required that had the ability to adjust the aperture (alas, among those ordered, not everyone had this ability, but luckily for me I came across a couple of them). In general, to improve your camera, it is advisable to have a varifocal lens with zoom and adjustable aperture. In practice, everything turned out to be as it was in theory - by closing the aperture, an increase in the depth of field was immediately visible, which made it possible to scan voluminous but small objects.
The main lens I use is mounted on the camera in the photo above. The second, with an adjustable aperture, is the largest, in the center. I use it for very small objects. The rest do not have a diaphragm, so I don’t use them - it turned out that these two are quite enough.
The plans now are either to find a webcam with a higher resolution (the quality and detail of the scans directly depends on the camera resolution), or to try to use some kind of digital camera with the ability to shoot video for these purposes - usually you can get a much higher resolution with them, and the lenses are better .
Actually, I could have ended there – I think I told you everything. I also thought that this was the end of assembling the scanner, but the further into the forest... While studying the forum of this program, I often came across various schemes of rotary tables - fortunately the software allows you to automate the scanning process. After one scan, a command is sent to the com port, the turntable rotates, rotating the object by a specified number of degrees, and gives a command for the next scan. As a result, with one click of the mouse we have circular scans of the object - it would seem, what more could you want? I tried this system with interest, but alas, I did not like this approach at all, and there are a couple of reasons for this.
1 – if an object has a complex shape, then simply rotating it will not be enough - you also need to tilt it different sides so that the camera and projector can reach all the depressions and other hard-to-reach places.
2 – even if there are no such places, and taking into account all the scans that were made, there are no parts left on the object that were not included in the scan, the question of the accuracy of the scan remains.
Let's say that some part of the model on one of the scans came out perfect. But this does not mean that on all scans in which this part was included, it also looks ideal, and when stitching scans from different angles, the result will be averaged, which cannot be encouraging. The program allows you to slightly edit the resulting scans (you can cut unnecessary part). If we rotate the model by 20 degrees, it means that after a full rotation we will have 18 scans, the part we need may well be present in half of them, therefore, in order to leave the best result, we will need to remove this piece from 8 scans... And such pieces with complex There can be a lot of models; as a result, almost half of each scan will be cut off, which is very labor-intensive and time-consuming.
Instead, it is better to immediately scan the surrounding areas after the first scan and check the result. As soon as one piece is ready, we move on to scanning the next one, and so on until the entire model is in perfect shape. This approach gives better results in less time.
But the question of convenience arises. Agree, it is inconvenient to try to manually rotate an object, looking not at it, but at the monitor - in order to control what is hitting the lens without changing the distance to the camera and the projector (so as not to lose focus). During another similar balancing act, I accidentally touched the camera, which accordingly threw off the entire calibration, and the whole process had to start over. I categorically did not like this arrangement, and after some thought I came up with a plan for such a structure (which, as you understand, I subsequently assembled).
This is not a turntable in the usual sense of the term. Thanks to this design, I can not only rotate the model, but also tilt it as I need. In this case, the center of the model remains in the plane of focus, but even if not, you can move the mount with the model back and forth.
All this was assembled on an Arduino, a small control program was written, and as a result, now I don’t have to get up from the computer when scanning - using the program, I change the position of the object being scanned, and at the same time, right there in the camera window, I select the optimal one for scanning angle
Entrails 
I included in the program the possibility of automatic scanning, as well as scanning not only in a circle, but with tilts of 45 degrees in one direction or the other, which gives three times more scans. However, in the end, I still never use this opportunity - it’s too inconvenient to then sort through the resulting pile of scans and clean them of unsuccessful pieces.
It is also worth mentioning some nuances of scanning.
1 – it is impossible to scan shiny and mirror surfaces. The light from them is reflected or gives such a glare that the program cannot correctly recognize the line. If there is a need to scan such an object, then such parts will have to be masked with something (washable paint, paper tape, etc.).
2 – it is more convenient to scan monotonous objects, since when setting the camera to a light color, the projector brightness is not set so high, the exposure is low, etc. And a dark-colored object requires more brightness, so if you have a multi-colored object, different parts of it will require different settings to get the best results. Here, too, it is more convenient to use scanning the object in parts.
3 – if you want to immediately get a color texture, then keep in mind that the camera and projector settings for the scan do not affect the settings for removing the texture (the scan is generally done in black and white mode), so play with the settings in texture mode the same way as you will do in scan mode.
My scanning process now looks like this:
- Focusing the projector and camera 
The projector light is too bright and the projected grid is not visible in the photo, but here is the view from the camera in the program 
Scanner calibration 
The calibration angle was made of metal plates, and calibration templates of different sizes were printed on magnetic paper - this way you can very quickly adjust to different sizes scanned objects.
View in the program 
It is recommended that the combined angle between the projector and camera beam be about 20 degrees. That's why this stand is used - when scanning large objects (for example, a person), the camera needs to be placed much further from the projector, but here they are standing close to me. The location of the camera relative to the projector can be only vertical or only horizontal - depending on the geometry of the object. In this case, the location is diagonal (13 degrees vertically and 36 degrees horizontally).
Scanning results from different angles. These are already cleaned scans, i.e. All unsuccessful and unnecessary parts (figure stand, mount included in the frame) were removed. 
Combining scans for subsequent merging into one object 
Due to the fact that each scan has its own color, it is convenient to control the correct alignment.
Well, after combining scans from different angles, we get the following models:
Miniature of Boromir from Lord of the Rings. 
When scanning a multi-colored object, the result is a little worse, unless you bother too much. But you can get an object with a texture right away :) 
Original models 
In the gallery of user works on the developer’s website (http://www.david-3d.com/en/news&community/usergallery) you can find many more interesting scans, people even scan fingerprints. And there are even scans of the same miniatures from Warhammer 
In conclusion, I would like to say that no matter what hardware you use, no matter how expensive a 3D scanner you buy, it is not a panacea for printing anything. Theoretically, of course, you can send the resulting object to a slicer and print it, but there are several reasons why you shouldn’t do this, and in any case it’s worth studying 3D graphics packages.
1 - Received scans, with good scanning quality (and we want to get best quality) have a lot of polygons. No, not even VERY a lot of. The scan of Boromir after the merger contained more than 8 million polygons - not every slicer will be able to work with such an object.
2 - Any objects bear traces of assembly and manufacturing. And if in reality, needle files and sandpaper are used to correct this (and sometimes there are still inaccessible places where it is impossible to use tools), then by working with a digital copy of the object, we can change it in any way we like - remove defects, improve detail, etc. .
3 - As I said at the beginning of the article, when I thought about a scanner, I didn’t want to print copies of objects, but change them as I pleased. I am not a sculptor, I do not have the tools, materials and skills to sculpt such a small model. But knowing how to work in 3D, it’s much easier for me to scan a similar Boromir and make him into some kind of Prince of Denmark.
By the way, this model already contains almost 100 times fewer polygons than the scan result.
Tags:
- 3d scanner
- diy or do it yourself
- 3D modeling
- 3D graphics
A professional 3D laser scanner will be unaffordable not only for you, but also for a large Hollywood studio. Of course, there are less expensive solutions, but their cost is expressed in four to five figures (in American dollars and European euros). But with some ingenuity, you can transform someone's face into the third dimension with just a simple overhead projector, a digital camera, and basic 3D software...
The whole complexity of the problem lies, naturally, in an additional dimension. If you needed a simple two-dimensional photograph of an object, all you had to do was take a digital camera, take a photograph of the object, and enter its image into the computer. It's a different matter if you need a three-dimensional mesh model - you'll have to work hard...
For a 3D artist, even objects that are quite simple at first glance can cause a lot of trouble when it comes to volume, color and surface texture. Therefore, before starting 3D modeling, it is necessary to acquire certain skills in this field, and it will take a long time before a beginner can begin specific creative work.
But even if you are familiar with 3D modeling firsthand, working with anthropomorphic objects, and even more so with human faces, seems to be quite complex and very time-consuming. 3D artists sometimes spend so much time making models of 3D people that they simply have no time left for other important work. But the animation of such objects is no less complex and time-consuming, and any flaws in modeling in this area begin to appear especially clearly and can negate the work as a whole.
Currently, there are various technologies for 3D scanning, and some companies even provide special services for preparing 3D models, but such solutions and services are not available to everyone, and the price of most of them is literally astronomical. However, by turning to such companies or using ready-made 3D objects, you may encounter insurmountable difficulties in the animation and rendering process.
The methods used to build 3D models may vary from project to project. Modeling a tractor or recreating a dinosaur is, of course, not the same thing. If we are talking about subsequent complex animation, then, undoubtedly, it is better to make the model “manually”, in some 3D package. The primary task in this in that case- build a correct working skeleton and create a neat and not too complex surface in structure. In the process of work, sculptures, photographic materials, rough drawings and drawings are widely used. It would seem, why not automate the modeling process? However various methods automatic digitization of objects (3D scanning) is not widely used. What is the reason?
Professional 3D scanning technologies
Let's first look at the most popular 3D scanning technology “for the poor” - the so-called chipping. Immersion Corporation specializes in 3D digitizers using this technology. Its MicroScribe 3D devices are affordable (ranging from $1,000 to $3,000, depending on the size of the object being processed) and easy to use, but they cannot digitize an object's texture (painting which is one of the most difficult parts of modeling). therefore, they do not radically optimize the process of making models so as to abandon manual work, and are used, as a rule, only if the 3D designer is insufficiently qualified.
In essence, such systems are a contact probe that, using several potentiometers mounted on a folding armature with hinged joints, records information about where the head is located, and transmits this information as coordinates in three-dimensional space when the corresponding button is pressed. It is enough to take the required number of measurements - and you have a ready-made mesh for modeling the surface of the future model.
But one of the main advantages of such systems is high degree control over the digitization process by the operator. Moreover, this device itself can be quite complex: for example, it uses a system of counterweights and automatic compensation for temperature changes and the corresponding expansion and contraction of the metal. When modeling, control lines are drawn on the original object with a pencil or marker; the operator then decides where to add detail to the mesh and where to leave the detailing to the 3D designers - it all depends on the purpose of the model. The purpose of such preliminary work is to ensure that the final mesh will be sufficiently accurate and as efficient as possible. When drawing on a model is impossible, you have to sculpt a model instead.
Moreover, after any digitization, quite labor-intensive processing in a 3D package will still inevitably be required, but with proper planning of the created mesh, such work can be significantly optimized even at the chopping stage. Unfortunately, more complex optical systems for digitizing 3D objects do not have this advantage (therefore, after their work, the object, as a rule, has to be re-modeled manually). However, optical systems have another advantage - they automatically “capture” the three-dimensional texture of an object, which can then be used with minimal modification. In this sense, laser, or optical, technology for scanning 3D objects is more advanced. Of the three main directions in which this technology developed (scanning by points, by zones and by stripes), best results showed the technology of scanning along stripes (usually with light markings).
The essence of this technology is that a light strip or grid is projected onto the surface of the model and its position is recorded by external video cameras. Gradually, as the model is scanned from one edge to the other, an accurate image of its surface is built and a three-dimensional texture is recorded.
The greatest success in the production of 3D scanners using optical technology has been achieved by Cyberware. Its first scanner with the pragmatic name Head Scanner (scanning only small objects such as the human head) was followed in the early 90s by the Whole Body Scanner and others. The technology turned out to be quite popular, and within a few years a whole a family of manufacturers of similar devices. Moreover, these devices work quite quickly and accurately (for example, scanning a head takes only a few seconds, and during this time 3D objects with half a million vertices are generated), but they still remain quite expensive (their price reaches half a million dollars) and have a number of serious shortcomings that lead to the fact that the models obtained with their help are completely unsuitable for animation.
The serious disadvantages include the following:
- the resulting models are very complex and heavy;
- problems arise with reflective surfaces (which is not surprising considering that light markings are used);
- the more complex the surface relief, the greater the likelihood of overlapping planes and close points, which 3D packages then refuse to work with;
- Since the process is completely automated, the 3D designer cannot influence it and only starts working when the scanning is completed.
The result is bulky objects that will require so much work to refine them that it is easier to model the object again.
Now cheaper scanners based on digital photography are also appearing on the market ($10-20 thousand), but their use is also slowed down for the reasons described above.
So in any case, your work will not be done automatically. We offer you a relatively labor-intensive and inexpensive “semi-automatic” procedure, following which, with a certain skill, you will be able to create high-quality three-dimensional models of any complexity.
So, let's look at how to get a model of a human face using cheap optical equipment...
3D scanning setup
Let's say you have a rather complex object from which you want to get a three-dimensional image in a computer. You will also need a slide or overhead projector (however, you can use a cheap slide projector, popular in the days of our grandmothers, if, of course, you can find one somewhere). In addition, you need a camera (preferably digital, in order to quickly transfer the resulting image to a computer). For a slide or slide projector, you will need to make a special “mask” that will project a vertical grating onto the object being photographed. You can, for example, take an exposed film and scratch thin parallel lines along it with a needle along the entire length of the frame. For an overhead projector, you can make a film with vertical lines applied to it in black ink (if the projector displays opaque sheets, then you can draw such lines on plain paper). We place the object to be scanned directly in front of the projector, and mount the camera on a tripod so that it shoots the object at an angle of 45°.
After this, we take two shots: the first with a vertical grid projected onto the model's face, and the second - just a photograph to obtain the appropriate texture. The projected lines should be located as close to each other as possible (from 0.5 to 1 cm) and should be clearly visible in the photograph so that you can confidently use them in the future when modeling.
So, we shoot: once with a projector, and a second time without it (you can simply cover it with a sheet of paper and control the camera remotely). If you have a digital camera, then it is better to immediately check the quality of the resulting image and, perhaps, repeat the series, moving or moving the projector closer to get confidently readable lines on the face in the photo. Naturally, a film camera is much less convenient - you will have to print photos and use a scanner to input the image into a computer.
Preparing the face frame
Once we have clear enough photos, we need to move into some kind of 3D modeling package. It would be better if there were sufficiently developed tools for spline or so-called NURBS modeling. NURBS is short for Non-Uniform Rational B-Spline. Choice modern programs quite large: from professional Alias|Wavefront Maya and 3DS MAX to cheap Hash Animation Master or Caligari True Space. The ideal choice for using NURBS modeling technology is Rhino 3D (or Rhinoceros).
Rhinoceros is a professional 3D conceptual design and modeling system for the operating room Windows environment 95/NT. The basis of modeling in this package is NURBS modeling technology. Rhino 3D lets you create, edit, analyze curves, surfaces, solids, and work with NURBS objects. The system works effectively with objects of any complexity and size. This can be either technical modeling - from a valve to a liner, or modeling of biological objects - from a mouse to a person. The functionality of the system puts it on par with top-level systems, while Rhino 3D compares favorably in price with other professional 3D modeling packages. Both novice users and seasoned professionals around the world prefer Rhino 3D, which is easy to learn and efficient to use.
One of the best techniques for modeling the head with splines is to use vertical curves that originate from the inside of the mouth. They extend from the mouth outward, following the facial features, and end at the base of the neck.
This approach is especially effective when you need to convey facial features with maximum accuracy and use facial expressions during animation. Since the direction of the curves usually coincides with the direction of the muscles, this construction greatly facilitates the animation of facial expressions. This applies primarily to areas around the mouth, which are the most mobile. In addition to our “automatic” stripes on the face, we will have to build a lot of additional curves. But before building them, it is recommended to study the various facial muscles and their purpose. By reading about these muscles, you can use a mirror to see how they act in different facial expressions, and accordingly discover the areas where you need maximum detail.
Let’s open our striped image, place it as a background in the appropriate window of the 3D package (it’s better if you prepare this window yourself by rotating the front projection by 45° and turning on perspective) and start modeling one half of the face. To create the basic shaping curves, we will use projected stripes, tracing them as efficiently as possible (creating the least number of control points). For such procedures, a lateral view is always used. Having completed tracing the stripes with curves, you can remove unnecessary dots and, on the contrary, add dots in the area of the mouth, nose or eyes. But, generally speaking, the curve we constructed should not contain more than two to three dozen points and most of them should be concentrated in the area of the lips, nose and mouth. However, it is not very convenient to insert additional points later when it comes to finer details. And remember that most 3D modeling packages that support so-called lofting or skinning tools (that is, those used to pull surfaces onto shape curves) prefer that all curves have the same number of points. However, some packages allow you to rearrange the curves so that they have the same number of points. This means you don't have to worry about it yourself. The total number of curves for one half of the face should also not be too large (as a rule, they are limited magic number 13). Remember that if you can keep the number of points and curves to a minimum, it will make facial animation much easier later on. Additionally, surfaces with fewer points and curves are smoother.
It is usually useful to create loft directly as you draw the curves (that is, gradually extend the surface from one curve to the next). Then you will immediately get a general idea of the final result and you will have hope to avoid unpleasant surprises later. Therefore, it is better to start tracing the curves sequentially, from nose to ear. If you are not aiming to make just a mask, then you should continue to draw curves from the front side of the object (using the photographed stripes) through the back of the head to the base of the neck (you can simply round the back of the head). Then you will have not only your face modeled, but your entire head.
If your package has a history option, like Maya or Rhinoceros, you can move the next curve points on the wireframe until you're happy with the appearance of the surface.
After lofting, the frame ribs should be visible. They should be smooth and not have sharp breaks. This will help you notice areas that may become problematic later on. This usually occurs where curves turn sharply.
The process of creating curves and fixing surfaces is most tedious when modeling a head, but Extra time, spent at this stage will save you from excessive efforts after the final skinning. Use Zoom more often to check the most critical areas.
NURBS curves
If you do not have sufficient experience in 3D modeling and cannot work immediately in three-dimensional space, we recommend using some auxiliary techniques. First, simply trace the stripes on the photo with NURBS curves (as a result, working on a flat photo, you will get spline curves on the plane). Then duplicate your working window (that is, the view of your window should match the neighboring one), rotate the view of the second window to 450 in reverse side(that is, the new window is a frontal projection of the future object) and turn off the perspective there. From this perspective, following the logic of the projection process, your curves should turn into vertical lines. So you must achieve such an arrangement from them without changing the correspondence of the curves to the lines in the original window.
Editing curves in a new window can be done with a simple function like Snap to Grid (or similar in your package). Additionally, this way it is possible to align the curves at a certain distance from each other (since they were supposed to be projected evenly). With this kind of editing, you can achieve a 3D look even without much spatial experience.
Use this method, although you cannot avoid slight distortions, especially in the area of the nose, lips and chin. You'll probably still need to edit some curves, reducing or increasing the density of control points, and make adjustments in 3D space.
Duplicating and flipping curves
Now that you are happy with the placement of the curves and the points on them, select everything except the central curve and double it. While the copied curves remain selected, flip them so that they go to the other side of the face. Starting from the middle curve, select them again, going around counterclockwise or clockwise. After that, create a final loft and close the object (for example, with the close function or similar). In Rhino, you can use the Surface from Curve Network function to generate a surface from curves. When the Tolerance and Edge Matching dialog appears, click OK. In Rhino, by the way, you can simply combine two sets of curves (for the right and left sides of the face).
So, the three-dimensional model of the face (or the head as a whole) is ready and now you can begin to finely edit it, making eyes, mouth, tongue, ears and other parts of the human body. Later, you can return to NURBS curves to refine the surface manually. Excess isoparametric curves (isoparms) can be removed manually using the Remove Knot function in Rhino or similar. If you are working with Maya, you can use Artisan to smooth the wireframe. At this point, you can deal with any problem points by manipulating the original curves or working directly with the surface rather than control points. Since you are now working on both sides of the face, you will have to select appropriate points on both sides. Most often, the move tool will be enough for you, but sometimes, when two points need to be brought closer together or further apart, the scale tool may be needed.
Texturing the face
The final stage involves shading the model using a second, normal photograph (without vertical stripes), using it as a texture map and mapping it onto both halves of the face to create a unified whole. This is your future texture map. Rhino (as well as other fairly professional packages) can apply flat textures to the model (via UV coordinates), but 3DS MAX or Maya do it better. Using special tools (flat map UV modifier), you can accurately select the place where the photo should lie on the model. However, you will still have to manually select, scale and mount the UV map on your 3D model. Just like when building a model, you will need to mirror the texture obtained from the photo onto the other half of the face. However, the texture of the face will be symmetrical, and since human faces never have exact symmetry, you will have to edit the second half of the face in some graphics editor to give it uniqueness, liveliness and authenticity.
Alternatives
The method we have discussed can only produce decent results if you have sufficient experience in 3D modeling. However, in any case, it will save you time and money that you could senselessly spend on some expensive 3D scanning device.
However, let's discuss possible alternatives. A fairly complex 3D model costs from $500 to $1,000 in the West, and fairly effective 3D scanning machines cost even more. Even such miniature systems as the Roland LPX-250 or the very primitive Minolta VI-700 photo scanner (which is practically no different from our system) cost several thousand dollars and do not at all guarantee decent results. And the prices of professional devices start from hundreds of thousands of dollars!
So the only alternative to our method is manual simulation, without using any hardware. However, in this case you will still need ordinary photographs, so why not also use your grandmother’s slide projector?
ComputerPress 11"2002
What characteristics of the part and how do they affect the complexity of scanning:
1. Size
3. Part material
Black, shiny, transparent surface requires preliminary application of matting spray. Thus, all products made of metal, glass, black or silver plastic are subject to matting. The spray dries, forming a thin chalky layer on the surface, which is then easily removed with a cloth or brush without damaging the product. Mobile phones and other equipment are also scanned using matting without affecting their functionality.
A white matte surface is considered ideal for scanning.
Example: matting the shiny lamp reflector.
4. Clean and even surface
If the surface of a part is dirty, rusty, or oily, it will have to be cleaned first to ensure high-quality scanning. Therefore, we ask customers to prepare parts for scanning in advance.
The surface is porous or uneven, there is a lot of debris during manufacturing (welds, artifacts and irregularities obtained during casting) - additional time for processing the scanned model.
5. Part configuration and surface topography
Simple is considered to be one-sided scanning of a flat part. When processing a scanned surface, the thickness is set.
A voluminous part requires scanning from all sides and turning over. At the same time, for high-quality automatic stitching, it is important that with each new scan the scanner “sees” part of the marks from the previous scan. Therefore, parts with thin sharp edges pose additional complexity.
Hard-to-reach places pose a particular challenge for scanning. Deep holes with different internal diameters and threads, cavities, and bending parts may not fall into the scanner's viewing area and will not be reflected in the scanned model. Such elements are measured and finished manually.
Manual measurements and error control are also required in the following cases:
- the presence of critical elements in the part (seats or interfaces, etc., where it is necessary to indicate specific tolerances and fits),
- applying a matting spray (which has its own thickness);
- errors in processing methods of a scanned part (for example, surface alignment at midpoints).
Example: shaft with cams (curvilinear surfaces with critical dimensions, increased complexity).
Complex surface topography ( a large number of curved surfaces, part elements) will not affect the complexity of scanning, but will greatly affect the complexity of processing, especially when constructing a solid model.
In addition, drawing such a part will also take more time than drawing a simple flat part.
Example: rotor wheel - places difficult to reach for a scanner, curved surfaces, especially difficult when constructing a solid-state model.
There are also flat, small and seemingly simple parts, but due to the large number of dimensions (cuts, holes, radii), completing the drawing becomes a labor-intensive task. In such a seemingly simple part, such as a blade, it is necessary to construct a large number of views and sections in the drawing.
Example: Flat frame with many holes.
6. The need to refine the 3d model
The task of restoring the wear of a part or the customer’s wishes for changes will necessarily require the construction of a solid-state CAD model with design modifications.
To estimate the cost of scanning a part, send a photo and short description tasks!
Today we will talk about the types and types of 3D scanners, as well as their effective use in various fields.
3D scanning is widely used in industry, medicine and everyday life. Moreover, many modern production processes cannot do without automation and control. In these cases, along with computer vision comes 3D scanning technology.
3D scanners can be divided into two types: Contact and, accordingly, non-contact.
Contact scanners
The first type of scanners includes CMM (coordinate measuring machines). These devices resemble industrial CNC machines, on a massive base, but instead of a spindle, a measuring head with a ruby ball at the end is attached. Scanning, or control of geometric dimensions, is carried out using the contact method. The probe slowly approaches the object being measured, registering the slightest touch.
There are also systems with moving “joints” in which high-precision encoders are installed. When the scanning organ is moved by the operator, these sensors record the movement of the entire system and, based on this data, build a three-dimensional model of the product.
An example of such scanners: Faro Arm Edge 9 - a compact and accurate industrial scanner ideal for monitoring molds or dies. And ROMER Absolute Arm SE 7 - a 7-axis measuring arm, extremely easy to use, equipped with a magnetic base that allows you to reliably attach the scanner to any flat metal surface. These scanners are widely used in high-precision production to control the geometric dimensions of manufactured products. Also, using these devices, you can perform a “full” scan and obtain a point cloud.
But this technology is not ideal and has a number of limitations, such as:
- Low scanning speed
- Unable (most often) to scan undercuts and small holes
- The installations are stationary and massive. Therefore, their use in 3D photography of landscapes and architectural objects is impossible
Non-contact active scanners
Contactless scanners are divided into several types based on the scanning method. Conventionally, they can be divided into laser and optical.
Laser scanners The majority of laser scanners operate on the principle of triangulation. The essence of triangulation 3D scanners is that a high-contrast camera searches for a laser beam on the surface of an object and measures the distance to it. In this case, the optical axis of the camera and laser are spaced apart, and the distance between them and the angle are known. Thus, through simple geometric measurements, we can quite accurately measure the distance to an object, quickly obtaining a cloud of points. Compared to scanners that measure beam response time, this class of devices has limitations in scanning range, but at the same time scans objects with high accuracy.
A striking example of such lasers are:
- BQ Ciclop - RUB 23,890, Accuracy: 0.5-5mm from part dimensions, Scanning area: 205 mm. There is a rotating platform.
- David Laserscanner - RUB 59,000, Accuracy: 0.5% of part dimensions, Scanning area: 10-600 mm.
- Digitizer (MakerBot) - RUB 93,100, Accuracy: 2mm, Scanning area: 205 mm. There is a rotating platform.
And also these scanners are already used for educational purposes in many Russian schools and universities. Another type of laser scanners include scanners based on measuring the response time of a laser beam from the surface of an object. These types of scanners are essentially a laser range finder. Such scanners are widely used in construction and landscape design and are successfully used to create 3D models of buildings and cultural monuments. They allow you to quickly digitize the surrounding space. Similar systems computer vision was even installed on the first prototypes of self-driving cars.
The main disadvantage of these systems is the difficulty in calculating the response time of the laser beam at short distances (less than a meter). Therefore, these scanners are mainly used by surveyors, landscape designers and architects.
It is also worth noting the accuracy and speed of scanning. The FARO Focus 3D scanner, costing $65,500, has a claimed accuracy of +-2mm at a distance of up to 25 meters. Scanning speed - 976,000 points/sec. Leica HDS8800 and Leica ScanStation P20 scanners have an accuracy of 2 to 20 mm at a distance of 100 and 1000 m. The scanning speed is up to 1 million points/sec. These scanning devices are ideal for surveying terrain and large objects and are not intended for scanning small parts.
Areas of use: Landscape design, Geodetic measurements, Construction of area maps, Scanning of cultural monuments.
Optical scanners
Moving on to optical scanners, I would like to note scanners based on the structured light scanning method. These devices consist of one or two video cameras in conjunction with a film projector. When the scanned object is illuminated with a “zebra” or black and white squares, which are arranged in a checkerboard pattern, the cameras analyze the curvature of the resulting image and build a 3D model based on this data. This method is widely used for reverse engineering, scanning jewelry, and is often used in medicine (prosthetics). It is especially worth noting the use of these scanners in prosthetics, since three-dimensional scanning and printing in this area works most efficiently. This technology allows you to make cosmetic, functional or dental prostheses as accurately as possible.
The disadvantages of this technology could include the limitation on the ability to scan large objects, but this problem is effectively solved by applying special markers to the object, which allow scanning large objects in parts with subsequent “gluing” of the model.
This scanning method is popular and gives excellent results, so there are quite a lot of such scanners on the market, here are some of them:
- RangeVision Smart - RUB 175,000. Scanning area from 150x112x112 mm to 500x375x375 mm, Accuracy: 0.2 mm - 0.1 mm.
- David SLS-3 - 299,000 rub. Scanning area from 10 to 600 mm, Accuracy - 0.05%
- Volume Technologies VT Mini - RUB 340,000. Scanning area - from 50 to 500 mm, Accuracy - 0.1%
- RangeVision Standard Plus - RUB 585,000. Scanning area from 66*50*50 mm to 850*530*530 mm, Accuracy: 0.015 - 0.16 mm
- RangeVision Advanced - RUB 710,000. Scanning area 66*50*50 mm to 850*530*530 mm, Accuracy: 0.03 mm - 0.16 mm. Camera resolution: 2MP
- RangeVision Premium - RUB 1,220,000. Scanning area from 66*50*50 mm to 850*530*530 mm. Accuracy: 0.015 mm - 0.16 mm. Camera resolution: 5mp
Areas of use:
Handheld scanners
It is worth noting that there are also portable hand-held versions of scanners that work using both laser and optical technology; usually these are professional devices with great accuracy and scanning speed. For example:
Areas of use: Reverse engineering, Education, Hobby, Computer games, Prosthetics, Scanning people, Architecture, Museum studies
Measurement control
One of the most popular areas for using 3D scanners is measurement control. In this direction, high-precision scanners are used, equipped with very precise cameras, projectors and specialized software for analyzing scanned products and comparing them with CAD models. For example:
- AICON stereoSCAN 3D – Scanning accuracy - 0.025 mm, scanning area - 400x400 mm.
- GOM ATOS Compact Scan 2M – Scanning accuracy - 0.021 - 0.615 mm, scanning area: 35 x 30 - 1000 x 750 mm².
- Gom ATOS Core 200 – Scanning accuracy - 0.03 mm, scanning area: 200 x 150 mm.
Non-contact passive scanners And the last scanning method that we will talk about is non-contact passive methods scanning. They exist in three types: Stereoscopic, Photometric and silhouette method.
Scanners that are based on the stereoscopic scanning method have two cameras rotated at a slight angle relative to each other. By analyzing the difference between the two images, a three-dimensional model is built. The accuracy of such scanners is not high, but they allow you to obtain a color three-dimensional model.
Also, when designing a car, a scale model is still made by hand from special clay, and then successfully scanned with similar scanners.
Areas of use: Not detailed reverse engineering
There are also more advanced solutions in this direction, this is photogrammetric survey, using the same principle as photometry is additionally used special system marks, allowing the program to determine with great accuracy from what angle and what part of the object was photographed and, as a result, to make a more accurate model. The highest quality such solution now has the AICON DPA scanner from AICON. Areas of use: Scanning large objects, an additional gadget to improve scanning accuracy
The silhouette scanning method is not widely used and has a number of disadvantages. To obtain an image, you need to place the scanned object on a contrasting background and take a series of photographs. Also, this method does not allow scanning concave surfaces.
There are also other scanning technologies, such as computed tomography (CT) and MRI, which uses X-rays, as well as conoscopic holography. All these scanning methods are quite highly specialized and do not relate to the topic of our article, so we will not focus on them in our review.
If you have any additions or questions, we will be happy to discuss them! Write in comments or email [email protected]
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