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(noob) caching irradiance

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I'm new to houdini/mantra rendering, so this might strike you as a noob question (i tried to find answers on this forum, but to no avail yet).

What I'm trying to do is to simple irradiance caching (similar to mental ray, which i use extensively, but i like the houdini/mantra approach too, very powerful stuff). I played around with the 'default' irradiance caching functionality in mantra (including tuning the parameters not published by default).

My experiences so far is that

1) when using irradiance caching, black 'spots' appear in the cached result (like a low pass filter is missing from the caching algorithm?).

2) one way to (partially) get rid of these black spots/artifacts is to increase the density of the point cache (reducing the min/max screen space radii), but this makes the overall rendering magnitudes slower than without caching.

Btw I'd need this for an architectural visualization project (which is an ideal testing ground for this kind of stuff, ie. all geometry are static, and there's only camera animation).

My goal is to cache irradiance (and possibly occlusion) to a point cloud, and use it for fast rendering. Mantra has some powerful pointcloud functions in shaders, so for the rendering part i don't anticipate any problems, but i don't know how to actually build the point cloud "by hand", if i can't rely on the "partially implemented" irradiance caching function.

I don't have any idea on how to calculate the irradiance pointcloud. I know occlusion can be done through SOPs (as it's geometry proximity, basically), but for indirect lighting i'd need to evaluate lighting and shading. Is it possible through SOPs? Or is it any way to use the regular irradiance caching without artifacts?

Anyway, I'd really appreciate some ideas to give me at least something to start with... Thanks!


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