Threads vs Memory Usage

[boogerlad]

Hello all, I have a question about Luxrender. Let's just say I have a fairly complex scene with thousands of triangles, a light, and a lot of different metal, plastic(transparent) and wood materials. How much ram would it require if one thread is used? Would ram usage go up as the number of threads go up in a linear fashion? Also, would using opencl for say a Radeon 7970 significantly increase the ram usage?

Thanks!

[SATtva]

How much ram would it require if one thread is used? Would ram usage go up as the number of threads go up in a linear fashion?

No, the number of CPU rendering threads has no practical impact on memory usage. The main contributing factors are: image buffer (for hires rendering with many lightgroups it can take quite a lot of RAM), hires textures and huge environment maps, integrator-specific buffers (mostly for SPPM and hybrid modes). Scene geometry is really low on the list -- you can fit almost 3 million polys in just 1GB RAM.

Also, would using opencl for say a Radeon 7970 significantly increase the ram usage?

Usually, yes -- hybrid rendering requires additional internal buffers to store state of rays being traced, and depending on Lux OpenCL settings it may take quite a lot of RAM.

[B.Y.O.B.]

Also, would using opencl for say a Radeon 7970 significantly increase the ram usage?

Usually, yes -- hybrid rendering requires additional internal buffers to store state of rays being traced, and depending on Lux OpenCL settings it may take quite a lot of RAM.

To lower hybrid RAM usage, use a smaller value for the ray depth than the default 48 - 16 should be fine.

[Dade]

Also, would using opencl for say a Radeon 7970 significantly increase the ram usage?

Usually, yes -- hybrid rendering requires additional internal buffers to store state of rays being traced, and depending on Lux OpenCL settings it may take quite a lot of RAM.

The additional internal buffers for hybrid rendering are also thread specific so if you double the number of threads you nearly double the amount of required ram (as written above, this doesn't happen with normal CPU rendering).