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Old 14th May 2008, 12:24 PM   #1
NCARalph
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Question How to control sculptie exporter

I got AC3D to do sculpties, and it works pretty well for some objects, but I've got a class of objects where there is a lot of detail in just a few areas, generally raised ridges. The problem is that there's a lot of distortion.

Subdividing helps, but not much. Stretching the texture map to give more space to the detailed area helps much more, but then there tend to be large and unpredictable distortions on the rest of the sculptie.

Is there any way to see what the control points will be on the sculptie and control them directly?
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Old 14th May 2008, 12:31 PM   #2
lisa
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Default Re: How to control sculptie exporter

The control points are determined by the UV space. ie. each texel in the the TCE represents a control point.
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Old 14th May 2008, 12:46 PM   #3
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Default Re: How to control sculptie exporter

ps. I'm working on an update but it's not done yet.
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Old 14th May 2008, 12:54 PM   #4
NCARalph
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Default Re: How to control sculptie exporter

Lisa - you are awesome! Your level of support here is pretty much unmatched.

Just to clarify, if each texel is a control point, presumably the exporter does something like combine nearest neighbors if there are too many. What does it do if there are too few? Repeat control points based on number of nearest neighbors or split texels based on number of neighbors, or something similar?

Obviously the mapping between object surfaces and texels can be distorted, but my understanding is the number and proximity of the texels is defined by the surfaces. Is that correct? That is, there's no other way to add or subtract texels than by editing the surfaces?

It sounds like I need to control the exact number and positions of my vertexes to get this closer to what I want.
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Old 14th May 2008, 02:20 PM   #5
lisa
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Default Re: How to control sculptie exporter

Happy to help.

Quote:
Originally Posted by NCARalph View Post
Just to clarify, if each texel is a control point, presumably the exporter does something like combine nearest neighbors if there are too many. What does it do if there are too few? Repeat control points based on number of nearest neighbors or split texels based on number of neighbors, or something similar?
Actually, neither. Internally the exporter has its own scanline renderer, the same one used by the texture baker in fact. It renders the shape in high resolution to a sculpt map using its own internal renderer, and then uses a filtered scale to bring it down to the number of control points that SL requires.

Quote:
Originally Posted by NCARalph View Post
Obviously the mapping between object surfaces and texels can be distorted, but my understanding is the number and proximity of the texels is defined by the surfaces. Is that correct? That is, there's no other way to add or subtract texels than by editing the surfaces?
Correct. Larger surfaces (in texture space, _not_ 3d space!) generate more texels than smaller surfaces, and by proxy more vertices when imported into SL.

In an ideal case, within AC3D you would have one vertex per texel, which is why extreme subdivision sometimes helps. If you don't have a vertex in the position of the sampled area, you will get a texel that's interpolated from the surface that crosses that space.

Quote:
Originally Posted by NCARalph View Post
It sounds like I need to control the exact number and positions of my vertexes to get this closer to what I want.
Correct. Number is less important than position in UV space. You want an even distribution of points in TCE, the more grid-like the better... in theory, if your vertices within the TCE are gridded exactly where the exporter samples, you should get exactly that point.

If it's helpful to visualize it, try switching to the wireframe view in SL (control-shift-R) and look at your imported sculpty. I have the base shapes sitting on the lawn behind the townhouses in Areumdeuli if you don't have any yet. Each vertex in the wireframe equals one texel in AC3D.
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Old 14th May 2008, 04:58 PM   #6
NCARalph
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Default Re: How to control sculptie exporter

Whew, as before, great great answers. Thanks.

Now I just have to use the info - how hard can it be.....
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