BodyPaint and ‘tags’

[Adam Trachtenberg]

I’ll give it a shot.

There are essentially two types of mapping — UVW, which maps textures based upon a flattened out mesh, and all the other options such as cubic, spherical, flat, etc., which project textures based upon parametric shapes, and in some cases based upon a shape (planar) and a direction (frontal, camera).

The UVW tag contains the UVW mesh information. You don’t need it unless you are using UVW mapping, and in fact you can save a lot of memory by deleting unnecessary UVW tags.

Primitive and nurbs objects don’t have UVW tags but they do have implicit UVW coordinates. When you make these objects editable the implicit coordinates are saved to a UVW tag.

If you delete a UVW tag you can, as you discovered, create a new one by right-clicking on a texture tag and selecting “Generate UVW Coordinates”. In that case, Cinema creates a flattened UVW mesh based upon the projection that’s selected in the tag.

As far as UVW manipulation goes, the rule is that the larger the UV polygon, the more resolution you will get. Imagine, for example, that you take one UV poly from a sphere and scale it so that it fits the whole UV canvas. In that case the whole texture will be mapped to that one polygon. Conversely, if you scale it waaaay down, that polygon will only be assigned a few pixels.

The best way to think of UVWs, in my opinion, is to imagine that the UVW mesh is wrapping paper covering your model, but not just any wrapping paper. It’s more like a thin rubber sheet that stretches to conform to the mesh. Imagine that you wrap the model and pattern on the paper/latex fits perfectly.

Now you have to flatten it out in order to paint on it (unless you want to paint on the model directly) but when you unwrap the gift you’ll find that the stretched parts simply won’t lie flat. In order to flatten it, you’ll have to cut into it, find a way to unstretch the stretched parts, or both. Otherwise you’ll just be squishing the stretched parts flat and the pattern that appears on those areas will look distorted.

There are a couple of goals to keep in mind when manipulation UVWs:

1. Scale appropriately to your needs: for example, if you have one texture for a human model, you might want to have the face UVWs scaled proportionately larger so you can paint more detail on the face. You might want to make the UV polys for the bottom of the feet very small if they won’t be seen;

2. Minimize distortion as much as possible: if you are trying to apply an existing texture to a model, it’s important to minimize distortion in the UVW mesh. Otherwise, pasting an undistorted texture on a distorted UVW mesh will result in a distorted projection as described above;

3. Keep related groups of UV polys together as much as possible: again this is more important if you’re applying existing textures to your model, or if you want to paint on the flat canvas vs. directly on the model.

Finally, it’s actually possible to have more than one UVW projection on a model. This is accomplished by using two or more materials, each assigned to a polygon selection. Each texture tag will use the UVW tag immediately to it’s right.

hth

[Alan Lacey]

Adam

I’m overcome with gratitude. Thanks very much for taking so much trouble to explain this. I hope some other members here will benefit from it as much as I do.

I’m working my way through 3Dkiwi’s (Nigel Doyle) excellent tutorial DVD that culminates with texturing a Spitfire and while it’s full of excellent information, some of this stuff is rather skipped over.

Alan

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