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Creating High Res Polygonal Models

Outline

I. Overview
II. What Are Smoothed Polygons?
III. Why Use Smoothed Polygons?

Advantages:
1. Simplicity
2. Intuitive interface (no stitching).
3. Speed of production.
4. Built in level of detail.
5. Single texture map for entire character.
6. All areas of the texture will be proportional to each other.

Disadvantages:
1. Requires UV layout
2. Cannot add or remove edges after laying out UVs with autoColor.
2. Resolution may not be high enough for some formats.
3. Less control over tessellating than with other surface types.
4. Doesn't work well with Maya Fur.
5. Texture seams.

IV. What technical problems are associated with smoothed polygons? How can I use History and MEL scripting to fix these problems

Problem 1
Too many vertices to skin the mesh once it is smoothed
Solution 1
Skin the low res mesh and add a polySmoothFace node after the skinCluster. Any blendShapes must come before the skinCluster

Problem 2
Poly faces with more than 4 vertices can produce bad results.
Solution 2
Model using Quads and Triangles.

Problem 3
UV distortion occurs after adding the polySmoothFace node.
Solution 3
Use projection nodes after the polySmoothFace node to lay out UVs on a reference object. Use MEL scripts autoColor, autoProject, and autoShellAssign to speed up the process.

V. Handing your model over to a character setup artist.
1. Production pipeline.
2. Merging the UV reference file with the setup file.
3. Hiding and locking the UV reference

Creating High Res Polygonal Models.

I. Overview

This tutorial will concentrate on how to use smoothed polygonal geometry to create high res models in Maya 4.5. We will be going over the advantages and disadvantages of this type of surface when compared to Nurbs or SubD surfaces. We will cover what sorts of technical challenges smoothed polygons present. We will use custom MEL scripts and History to overcome these challenges on your character model. Finally we will cover how to implement this type of modeling in a production pipeline. And I will show some tips on how to work with a character setup artist to merge your final polygonal model and textures into a well organized character reference file.

II. What Are Smoothed Polygons?

Smoothed Polygons are a low res Polygonal mesh with an adjustable polySmoothFace node in their history. To create smoothed Polygons use the Polygons - Smooth command in the modeling menu set of Maya. A popular technique is to use a low res mesh to control a High res mesh by connecting their shape and smoothing the result. There are also several free MEL scripts available to edit polygons in this manner Such as connectPolyShape by Dirk Bialluch. Or you can simply edit the low res mesh, add the polySmoothFace, and use the deleteInput MEL script to remove the smooth when you want to reedit the low res mesh.

The resulting mesh is still just polygons. However it will now be much denser and will have a polySmoothFace in it's history. By using the polySmoothFace node you can create a level of detail which would be difficult to attain simply by adding edges manually. You should not move any vertices on the mesh after it has been smoothed.

Note that there are now 2 different smooth algorithms in Maya 4.5. The exponential setting works best with the scripts we will be using in this tutorial. I will be using the exponential setting for all the examples.

III. Why Use Smoothed Polygons?

Advantages:
1. Simplicity.

Polygons are the oldest type of geometry in 3D computer graphics. What you see is what you get, There is no tessellation or parameterization necessary. It takes less computation to calculate a flat plane made out of polygons than one made out of NURBs.

2. Intuitive interface.

Most artists can pick up modeling in smoothed polygons within a few days. Because the mesh is all one piece tangency between patches is not an issue. Stitching is not necessary. During the modeling process edges and faces can be added or removed quickly and easily. Although it is always a good practice to start out with the general shape of the model and continuously add detail The order in which geometry is created is much less precarious than with a Nurbs model. Where Nurbs Modeling requires a high degree of practice and skill to learn the correct order of steps in Modeling. Modeling in Polygons is more like fighting your way out of a wet paper bag.

3. Speed of production.

Models can be built much quicker in smoothed Polygons than in NURBs patches. Most Character Models take between 1 and 2 days.

4. Built in level of detail.

The divisions attribute of Maya's polySmoothFace node can be adjusted at any time. This creates a built in level of detail which can be adjusted depending on the distance from the camera to the model.

5. Single texture map for entire character.

Using a polygonal model allows for the use of a single texture map for the entire character. This makes working on file textures in Photoshop much more simple and intuitive than working on multiple texture maps for a patch model.

5. All areas of the texture will be proportional to each other.

Using the custom MEL script autoProject we can keep each shell in the UV texture editor proportional to each other. This keeps the scale of texture maps consistent across the entire surface.

Disadvantages:
1. Requires UV layout

NURBs patches already have UVs embedded into their geometry. Provided that a model is well built in NURBs a texture artist can begin texturing as soon as the modeler hands him the finished model. Before smoothed Polygons can be textured an artist must go in and manually create UVs this generally adds anywhere between a few hours to a few days to the production process.

2. Resolution may not be high enough for some formats.

Despite all efforts to pack the UV texture editor tightly and use areas of a map more than once the UV map of a smoothed polygonal model almost always contains Unused space. The result is that Texture maps on a smoothed polygonal model must be larger than maps on a Nurbs model to achieve the same amount of resolution.

3. High poly count on smooth level 2.

Using smoothed polygons you have much less control over the smoothness of the mesh than if you used NURBs. On smooth level one the model may appear slightly faceted. Smooth level two however increases the face count on a model exponentially and often overshoots the number of faces that is actually necessary.

4. Doesn't work well with Maya Fur.

This type of model just doesn't work well with Maya Fur. The ability to brush the fur in an intuitive manner is severely compromised on polygonal models. NURBs models are far superior for use with Maya Fur.

IV. What technical problems are associated with smoothed polygons? How can I use History and MEL scripting to fix these problems

Example File: CylinderSkinExample_01.mb

Problem 1: Too many vertices to skin the mesh once it is smoothed.

Once you smooth a polygonal mesh and delete it's history it becomes extremely difficult to bind that geometry to a skeleton. Although it is technically possible to set skin weights on all the vertices of a smoothed mesh it would be extremely labor intensive and inefficient.

Solution 1: Skin the low res mesh and add a polySmoothFace node after the skinCluster. Any blendShapes must come before the skinCluster

One solution is to skin the mesh before it is smoothed. This allows the character setup artist to only set weights on the much lighter low res mesh and smooth the geometry when he is done. Any blendShapes must be added before the skinCluster.

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