Creating High Res Polygonal Models
Problem 2: Poly faces with more than 4 vertices can produce bad results.
Faces with more than 4 edges or N-sided faces will cause unpredictable results when they are smoothed. Even worse when they are animated they may cause popping in the mesh.
Solution 2: Model using Quads and Triangles.
For this reason it is advantageous to model primarily in Quads and Triangles. Use N-sided faces as sparingly as possible. Definitely try to avoid these faces in areas that will be deforming heavily such as elbows, knees and the area around the mouth. The MEL script quadChecker can be used to color each face on a polygonal object based on its number of edges. Quads are green. Triangles are blue. And N-sided faces are red.
Problem 3: UV distortion occurs after adding the polySmoothFace node.
Example file: sphereExample_01.mb
If you look in the UV texture editor when you add a polySmoothFace node to your mesh you may notice that the position of your UVs stays the same and the edges created by the smooth subdivide the preexisting edges. This is a problem. The UVs you now have are confusing in that they look similar to what a good UV set would be. However on closer inspection you will notice that they are no longer an accurate representation of your mesh. The surface you now have is curved while your UVs remain straight. This results in UV distortion. The extent of this distortion can range from very slight to severe depending on the original geometry of your mesh.
Solution 3: Use projection nodes after the polySmoothFace node to lay out UVs. Use MEL scripts autoColor, autoProject, and autoShellAssign to speed up the process.
By using polygonal projections after the smooth node we can eliminate this distortion. Because the projections come after the smooth in history they will automatically update when the smooth level is changed. This will create an accurate representation of the surface we will eventually be painting on. It also will create a UV map that will automatically update on any smooth level.
If the model you are painting on is totally flat this process is going to be easy. You will only need one projection. But how can we deal with a curved model containing faces that point in multiple directions. Won't there be texture stretching in areas that face away from the projection?
We will need multiple projections coming from different directions to eliminate texture stretching. Faces need to have their UVs created by projections coming from the most advantageous angle. Faces with a normal facing down the positive Z axis need to be projected from the positive Z direction. Faces with a normal facing down the negative X axis need to be projected from the negative X direction.
But how do we determine which faces get included in which projection? We need a way to pick faces on a complex polygonal object and tell Maya which direction we want them to be projected from. A common way to do this is to smooth the model and then select faces on the resulting high res mesh and project onto them. Selecting these faces is difficult because of the density of a smoothed polygonal mesh. In addition the UV map created will function on only one smooth level eliminating the built in level of detail we created by adding the polySmoothFace
By creating selection sets on the low res model before the polySmoothFace is added we can break up the model into areas which will use different projections. After the model is smoothed these selection sets will include the new faces that result from the originals. It is easier to use this method because there are less faces to select on the low res model. Because the selection sets will update when the smooth level of the mesh changes the built in level of detail is preserved.
A disadvantage of using regular selection sets is that there is no quick way of telling which faces are included in the set without selecting it. For this reason it is advantageous to use a special type of set called a shader group to make our selections. The main advantage of shader groups is that they are linked to a shader which can change the color of the faces in the shaded view. This can give artists a quick visual representation of which faces are included in which set. Assigning a shader to a face automatically forces that face into the shaders corresponding shader group. Also a single face can only be contained in a single shader group. Assigning it to another shader removes it from it's current shader group. This is an excellent way to set up face selections to be used with projections
