Read Constructing the Inspired Character — Part 1 [2] and Part 2 [3]
This excerpt is the next in a number of adaptations from the new Inspired 3D series published by Premier Press. Comprised of four titles and edited by Kyle Clark and Michael Ford, these books are designed to provide animators and curious moviegoers with tips and tricks from Hollywood veterans. The following is excerpted from Modeling & Texture Mapping.
Facial Animation and Blend Shapes On this production, despite my best efforts to avoid this, the production decided early on that the facial animation would be controlled using blend shapes. Blend shapes are 3D morph targets that have the exact topology as the face they are controlling.
Full Face Shapes vs. Local Face Shapes
In the production of an animated character, the character can have the face animated in two basic ways. One way is to have animation setup control the face using various setup techniques. This requires expertise on the part of the setup technical directors. In a large production facility, the efficiency of scale can make difficult jobs like this commonplace. Many characters have already been set up that can be taken apart and reused. In a small production, the process of creating facial controls can be time consuming. This is especially true because no other similar characters can have their controls “recycled” for the new character.
In the creation of face shapes for an animated character, there are two basic schools of thought regarding the way the face should be animated using blend shapes. One method is to use the entire face as a specific target. If the character is going to frown, then the entire face is sculpted into a frown shape. The eyebrows are sculpted into a furrowed appearance, and the entire mouth is sculpted into a real scowl.
[Figures 36-41] Blend shapes that affected larger, less localized areas of the face.
Face targets like this are normally sculpted to the maximum range, which can be used as the production dictates. If the shape is a 100% frown, then the production can use this shape in increments of 20%, 40% and so on, to create frowns of less intensity.
Local face shapes are broken down into specific regions. These regions are separated into left, right and center regions. If there were a smile to be modeled, the blend shape would be a left smile, a right smile and a center smile. This gives the animator a lot of control as to what part of the face will be affected by the blend shape.
For this project, the local blend shapes were a necessity. But because I know that the vast majority of animation time using blend shapes was spent trying to get multiple blend shapes to animate as a single channel, I also added some blend shapes that took up an entire region. I modeled a left smile and a right smile, and I also modeled an overall smile as well. I modeled a left furrowed brow and a right furrowed brow, and I modeled an overall furrowed brow.
The jaw was to be animated using a skeletal setup. The jaw position is not animated using blend shapes. The modeling of the blend shapes had to be coordinated with the animation of the jaw. Figures 36 through 47 show the jaw in various stages of being opened or shut along with the blend shapes being shown. This helped visualize how the blend shapes would behave during the modeling process.
I was careful to try to keep the mouth blend shapes from affecting any other regions, and the eye blend shapes localized to the eye region. In this way, these particular shapes were hybrid global/ local blend shapes. They affected an entire area, but only the area intended to animate, not the entire face.
When I was creating the localized blend shapes, the areas that were affected stayed on one side of the face. There were many shapes not shown here that broke each part of the face into even smaller regions. These regions were isolated to areas like one eye (Figures 42 and 43), one eyebrow (Figure 45), or one corner of the mouth (Figure 46).
Most blend shapes are modeled about 20% past the most extreme point where the animator is expected to use them. This allows for more elastic animation and gives greater flexibility when combining blend shapes.
[Figures 42-47] Localized blend shapes.
Shapes and Phonemes The complex shapes required the modeling of the frown, smile, furrowing, puckering, pouting, yawning and kissing.
These shapes include mouth smirk, mouth sneer, mouth dread, mouth wince, eye furrow, eye squint and mouth smile.
The mouth regions were extended to include the cheeks, and the eye regions were extended to include the forehead and eyebrows.
The decision of which shapes to build came from two primary sources. First, Rick Grandy, the technical editor for this book, came up with a preliminary list, and then the animator, Kyle Clark, came up with some items that he needed to get this project done. Overall there were 66 targets built for this animation, and there will probably be some more that need to be built as more animation is done. Some models used for production have more than 200 blend shapes modeled. The face shapes were broken down by region:
Phonemes are face shapes directly related to speech. Different theories exist as to which phonemes are required for animation of speech. Thirteen accepted shapes are recognized as vismemes, which are used in the creation of English speech. These shapes are as follows:
For the list of shapes that would be modeled for this model, the phonemes were reduced to eight basic shapes:
Wire Deformer Rig for Face Shape Creation Another thing that was working in my favor, in a big way, was that the model being manipulated was a low-resolution cage. This version of the model was very fast to edit, and the smoothed results always looked better than if the model had been edited in high-resolution.
During the process of modeling blend shapes, the animation rig that had the jaw rotation skeleton was used to ensure that the rotation used for the blend shape jaw matched the rotation used by the jaw on the actual animation rig.
For the purposes of creating a fast way to create blend shapes, I created a wire deformer rig. The wire deformer makes the creation of expressions very quick. By manipulating the points on the curves, I was able to move the surface of the skin in a very elastic, natural way.
Cleanup and Testing
The modeler needs to test and clean up blend shapes after making them. Testing blend shapes is a critical part of the modeling process. Many things can go wrong during the creation of blend shapes. Any time the model is exported from Maya in another format (like .obj) will scramble the order of the polygons in the model. Anything that affects polygon ordering will create many problems.
When testing the model, the modeler should be looking for technical problems as well as aesthetic problems. The technical problems will become evident quickly and require no additional discussion.
The aesthetic problems include the following:
UVs There are many methods for applying UVs. For this section, the basic application types will not be discussed. In order to texture this model, there were two primary methods employed in the application of UV coordinates. One method was used solely on the head, and the other method was used on the rest of the character.
In order to get the character rendered, the modeler needs to apply UV coordinates to the character. The process of editing UVs has a fairly straightforward goal: Will the texture artist be able to paint textures on this character that will not twist or deform unnaturally?
When unfolding UVs on a model, several things need to be accomplished:
UV Editing Using Texture Maps These maps are useful during the initial unwrapping stage because the unique pattern helps establish which areas are overlapping, are being repeated, or are twisted. Because each numeral or color combination only appears once, checking for repeating numeral or color blocks can help eliminate overlapping and tiling.
The best way to check to see if the UVs are working correctly is to preview the UV work using a texture map on the model. Different maps accomplish different things while unmeshing the UVs on a production model. These maps can be used in progression to work out the UV mapping issues one step at a time. The most common test maps, shown in progression, are:
1. A color and number grid. These maps are useful in the initial unwrapping of UVs on a model. Several maps of this type are commonly available. The map shown in Figure 13.49 is a map I made in Photoshop in about 15 minutes. Maps such as these are designed so no numeral (or letter, depending on the map) will fall in the same colored square twice throughout the map. This map has 10 numerals used 10 times each. The placement of the numerals in rows helps establish orientation while viewing the map on the model. The colors are more random but at the same time are somewhat organized diagonally, also helping to establish orientation.
2. Checkerboards or grids. These maps are useful in getting the excessive twisting and deformation out of the UV set in a model. The colored grid can be distracting to view and can hide many problems associated with UV work. By using a less distracting pattern that has evenly spaced partitions, the modeler can check for twisting and stretching much more easily.
In the example shown in Figure 54, the noise map is applied to the model. This map in Figure 54 was generated in Photoshop using the texturizer filter in about a minute. In previous tests, the mapping seemed fine, and the stretching was minimal. After the noise map is used, the stretching in the ear and across the nose is easily apparent (Figure 55). The stretching inside the mouth is really out of control, but that is an area that will not be seen, so it will normally not have to be as accurately mapped and modeled as the rest of the head.
It will be helpful to view these textures in realtime so rendering is only used for a final test. Real-time texture viewing will speed up the UV editing process dramatically. Unfortunately, procedural textures do not update in real time; they can only be viewed using a software render. Most graphics cards are optimized to accept bitmapped or file-based textures. A file that has a grid or checkerboard in it can be assigned to the model, and the file-based texture will update in realtime if the modeler is on a machine with a decent graphics card.
3. Organic noise patterns. The noise map is the acid test for fine-tuning the UVs so there is no stretching. By the time the noise map is applied, there should be no overlapping UVs or twisted UVs; the noise map will not be able to help identify those problems. The noise map does one thing, but it does it well. The noise map shows stretching.
[Figures 56 & 57] UV coordinates for the low-resolution head (top). Subdivided polygons allowed the UVs to be transferred to the high-resolution head without any additional work (bottom).
Face: Relax From this starting point, the individual vertices were pulled manually within the UV texture editing window along the texture edges to line up with the UV borders, ensuring that the exterior vertices did not go beyond the 0 to 1 boundaries.
From that point, it was important to ensure that the overlapping areas within the ear, mouth, nose, and eye sockets were all flat and clean. This was done by pulling some of the points in these problem areas to the hidden interiors of these areas. The places in the eye socket, mouth, nostrils, and ear inner are safe places to hide a lot of things. The overlapping UVs in the eye socket were pulled to the center of the eye, the mouth interior was pulled to the interior of the mouth, and so forth.
The UVs inside the eye socket were selected in the 3D modeling window (finding them in the texture editing window is too confusing). When the relax function was applied the these UVs, the UVs averaged themselves evenly within these safe zones. The head was split at the top because the hair would cover the top of the head, and I did not need to worry about matching the UVs in that area.
Other UVs that needed relaxing were also carefully selected in the modeling window and relaxed in the texture editing window. The fastest way to do a job like this is to simply grab all the UVs and relax them all at once. The problem with this method is that all the UV spaces are averaged out to be the same size. There will be excessive detail in areas that have smaller polygons and not enough detail where the polygons are spread out.
The face was done simply by starting with a cylindrical texture coordinate system. This provided a basis for unfolding the texture that allowed the small polygons in the eye area to remain small, and the large polygons on the side of the head to remain large.
[Figures 58 & 59] The UV coordinates for the shirt. Note the uniform parameterization along the front and back (left). The UV coordinates of the arms and hands (right).
Body Parts: UV by Hand For the most part, the application of UVs using a texture mapping tool was simply a formality. The texture coordinates for these body parts had to be completely modeled in the UV texture window to achieve uniform parameterization. Manually adjusting the UVs into this uniform configuration was a tedious task and took about as much time to do as the modeling of these simple body parts.
The body was a much simpler model in many ways. The problem with getting UVs on simple geometry like this is that there are no default methods for applying UVs to these polygonal shapes that will make the textures wrap onto them as easily as they would if there were NURBS shapes. It doesn’t take long to texture map simple tubes if they are NURBS surfaces, because the parameterization is inherent in the surface itself. Using polygons to create these parts of the body posed an additional challenge of getting these parts to map smoothly.
The completed UV work is shown in Figure 60. The checkerboard texture lines up evenly across the body, the legs and the arms.
The Eyes
The eyes were mapped using a single map for the iris. The interesting part of this part of the character is the way the specularity had to be handled. I was trying to achieve a specific look, and using an anisotropic shader provided me the kind of specular sheen I was in search of. The problem with this was that the specularity spread all over the eyeball, causing it to look really glowy and weird. I used a specularity map to keep the shininess only in the iris — that was the end of the weird glowing eyeballs.
Every character model presents different challenges. When the production pipeline differs than the example shown here, different techniques should be employed for some of the steps illustrated here. The methods used in this tutorial to create blend shapes and texture UVs are very universal and are useful for all character models. The final model shown in Figure 62, shows the texture maps created by Lopsie Schwartz, the animation set up created by Michael Ford and Alan Lehman, the animation pose created by Kyle Clark, and the model and lighting that I created for the cover of the book.
To learn more about character modeling and other topics of interest to animators, check out Inspired 3D Modeling and Texture Mapping by Tom Capizzi; series edited by Kyle Clark and Michael Ford: Premier Press, 2002. 266 pages with illustrations. ISBN 1-931841-49-7. ($59.99) Read [5] more about all four titles in the Inspired series and check back to VFXWorld frequently to read new excerpts.
Tom Capizzi is a technical director at Rhythm & Hues Studios. He has teaching experience at such respected schools as Center for Creative Studies in Detroit, Academy of Art in San Francisco and Art Center College of Design in Pasadena. He has been in film production in L.A. as a modeling and lighting technical director on many feature productions, including Dr. Doolittle 2, The Flintstones: Viva Rock Vegas, Stuart Little, Mystery Men, Babe 2: Pig in the City and Mouse Hunt.
Series editor Kyle Clark is a lead animator at Microsoft’s Digital Anvil Studios and co-founder of Animation Foundation. He majored in film, video and computer animation at USC and has since worked on a number of feature, commercial and game projects. He has also taught at various schools, including San Francisco Academy of Art College, San Francisco State University, UCLA School of Design and Texas A&M University.
Michael Ford, series editor, is a senior technical animator at Sony Pictures Imageworks and co-founder of Animation Foundation. A graduate of UCLA’s School of Design, he has since worked on numerous feature and commercial projects at ILM, Centropolis FX and Digital Magic. He has lectured at the UCLA School of Design, USC, DeAnza College and San Francisco Academy of Art College.
Links:
[1] http://www.awn.com/imagepicker/image/6945
[2] http://vfxworld.com/?atype=articles&id=1992
[3] http://vfxworld.com/?atype=articles&id=2004
[4] http://www.awn.com/imagepicker/image/6946
[5] http://www.premierpressbooks.com/ptr_searchResults.cfm?searchText=Inspired&submit=GoImages/Captions
![[Figure 48] indicates where the curvers were drawn to create the wire deformers used to edit the model for blend shapes.](http://www.awn.com/files/imagepicker/1/i3D48_13-48.jpg)