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View Full Version : Aligning displacements in various render engines

marcuso
10-25-2009, 08:06 PM
Just posted this on odforce, but would like to hear from you guys aswell.

I'm planning on doing a couple of my passes on varying render engines. More specifically, hardsurface shading in maxwell, an SSS from mental ray and AOV's from mantra.

Very important that the displacements in these engines match up, but using a 16-bit displacement from zbrush, I'm having trouble figuring out how to do it, since they seems to be pretty much relative to their enviroment. I'm guessing a 32-bit map would make it easier, but there's still the scale factor to worry about and, most importantly i guess, they all slice up the polys differently. With enough polys, that probably wouldn't matter.

So, how would you align the displacement in these cases, and what factors play important roles in the precision of it?
cgbeige
10-25-2009, 10:39 PM
I just recently learned myself that a 32-bit displacement map is absolute and doesn't suffer from the scaling problem like 8/16-bit displacement maps do. I've only been able to test it with VRay but it was true. I have no idea how it does this – must be some proportion respected and known by all renderers when you use 32-bit displacement maps.
marcuso
10-26-2009, 06:03 PM
Actually, 32-bit displacements have their gray-value=no displacement set at 0, instead of 0.5 like 8/16-bit. Going from -1 to 1, always. However, in 8/16-bit displacements, zbrush, and I believe mudbox, automatically optimizes this range. Say, if you only sculpted downwards, there would be no need for the upper half of the 0-1 range, thus it shifts the midvalue to .1 or whatever, putting more information in the file to use. Thats where the magic alpha gain/alpha offset values come from. The 32-bit variant has enough information to go around, and doesn't need to to that, thus always staying within -1 and 1.

Using 32-bit would probably solve my problem, but the files get a lot bigger and I don't need such precision atm.
marcuso
10-28-2009, 02:11 AM
bump, anyone?
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