Direct Light Sampling

[b-tag]

Hi,

When I render with Direct Light Sampling on or off, I get quite different results for the scene below. It is the default cube with a simple glossy material, lit by a HDRI:

Direct Light Sampling: off

Direct Light Sampling: on

So, which is the correct result?

Since I can't say whether this is a render, exporter, or Blender issue, or ultimately there is something wrong with my scene, I have attached the .blend file for you to give it a try. The HDRI is #7 from this pack, but I'm pretty sure any similar set-up would do.

For a reference, I'm using is LuxRender_CVS_20120111_64bit_OpenCL with Blender r43433 x64 on Win7 x64.

[jeanphi]

Hi,

If bright parts of the HDRI are mostly off the specular reflection direction, then disabling direct light sampling will make it very hard to get light from those prominent areas, leading to a darker appearance until it eventually finds something brighter, but then it will cause a lot of noise.

Jeanphi

[b-tag]

So this option can be quite useful in rendering quick initial previews, etc. Nice.

Thanks,

b.