Baking ambient occlusion on NURBS

[jrx]

Hi Everyone.

I have a mid-complex scene, but modelled almost entirely out of NURBS surfaces. Since ambient occlusion pass takes up most of rendering time and my scene is mostly static I thought about baking it to a texture. I have created some simple uv layouts, set up baking ROP, and used convert to convert objects to polygons. But it appeared that convert does not play very nice with uv coordinates and generates some errors. Maintaining two versions (poly and nurbs) of uv's and taking care of their coherence seems pretty painful. I also get some strange artifacts, I am not sure where they come from. Is there any good way of baking ambient occlusion on NURBS?

[symek]

I don't recommend rendering of nurbs at all. They almost always render much slower than polygons. I think you should consider reapplying uv on converted geometry to fix any issues. I haven't baked occlusion for ages, so I can't help in respect to this, except I usually used high quality irradiance cache for a static backgrounds, not texture baking. Currently nice PBR settings enough high just for diffuse light (easier) with a little help of photon map would allow to avoid baking at all.

hth,

skk.

ps Studiowałeś na mismapie? Czym się zajmujesz, jeśli wolno spytać ?

Edited June 3, 2011 by SYmek

[brianburke]

if you bake to point clouds you don't even need uvs... and that will work fine with nurbz.

[symek]

True, point clouds may help also, although I tend to avoid them (for baking), since initial good results too often finalize with artifacts and headache . Albeit most often at the sharp edges, thus nurbs might stand it.

[jrx]

I have played today already a bit with mantra's build in irradiance cache and I must admit it works amazingy well. I have found somewhere information about people saying I can have different irradiance cache for different objects (?), but I haven't found how to set that up. Have you got any experience with that?

I will also try to explore other possibilities to have a better comparison of different techniqies. I haven't found yet too many materials regarding using point clouds in VEX, are there any good?

[symek]

I have played today already a bit with mantra's build in irradiance cache and I must admit it works amazingy well. I have found somewhere information about people saying I can have different irradiance cache for different objects (?), but I haven't found how to set that up. Have you got any experience with that?

You just have to add all relevant parameters for every object you want to treat separately. Edit Rendering Parameters by Gear icon on Object nodes, and add all in Irradiance folder. High quality setting in my case were usually:

Irradiance Error: 0.001

Min/Max spacing: 5/0.01

In typical scenes speed up is around x5.

I will also try to explore other possibilities to have a better comparison of different techniqies. I haven't found yet too many materials regarding using point clouds in VEX, are there any good?

Read all about point cloud related functions in Help: http://www.sidefx.com/docs/houdini11.0/vex/functions/pcopen

There are some code snippets spread around in various places. Also old, but still relevant presentation from 2005:

http://www.sidefx.com/exchange/info.php?fileid=208&versionid=208

hth,

skk.