Dumb question : Fastgi

[edward]

Hmm ... they sound subtly different from mantra's point clouds. In mantra, you just generate a bunch of points (in SOPs) and then you have some functions in the shader which let you read/write attribute data (ie. shader variables) from the points. At each point, you can easily to do fast look up of all the points within a given radius. I think it's closer to the volumetric stuff of prman's.

[Jason]

For prman, the way to acccess these pointclouds is to create a Brickmap (those volumetric textures) out of them and read that in a shader. Whenever someone learns that in Mantra you can access pointclouds directly, they go ooooh! It would still be good to be able to write out data from our shaders - to in effect make a precomputed cache. I'm not too sure about what API prman provide for accessing/creating pointclouds and brickmaps.

[dmaas]

PRMan 11.5 supports point clouds only. PRMan 12 supports point clouds and brick maps. (brick maps are created from point cloud files in a post-process, the same way that texture maps are created from image files). The PRMan 12 API for writing point clouds is bake3d(). The API for reading brick maps is texture3d(). These are both generic and can read/write arbitrary data. (in PRMan 11.5 point clouds could only be read and written by special shade-ops like occlusion())

Brick maps are faster to access and use less memory (since they are tiled like texture maps). However I have had problems getting "smooth" results from brick maps so I mostly stick to point clouds.

[Daniel]

Brick maps are faster to access and use less memory (since they are tiled like texture maps). However I have had problems getting "smooth" results from brick maps so I mostly stick to point clouds.

15602[/snapback]

I'm just getting into the prman12 stuff now, looking though the docs and trying the examples. I see how to access the brickmaps from a shader, but I'm unclear how to access point clouds directly w/out going to a brickmap?

daniel