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Luminous walls with -ab 0

asked 2019-03-22 14:59:47 -0500

Determinant's avatar

updated 2019-03-22 15:01:54 -0500

I created an HDR image in Radiance of a room with sunlight coming through a window. I set -ab 0, but the walls seem to be reflecting light. With this setting, shouldn't the window be the only "source" of light? What's more, even when the simulated sunlight has barely "risen", the walls seem to be equally luminous. Are these walls somehow becoming sources? Any insights?

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Can you provide the full set of parameters that you are using? I'm specifically wondering if you are setting -av 0 0 0.

Nathaniel Jones's avatar Nathaniel Jones  ( 2019-03-22 15:41:47 -0500 )edit

@Nathaniel Jones that's exactly what it was. I actually took the -av parameters completely out and now I have the results I'm looking for. I think I don't really understand what -av does. If you post your comment as an answer, I'll mark it as the answer. Thanks a bunch.

Determinant's avatar Determinant  ( 2019-03-25 15:42:45 -0500 )edit

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answered 2019-03-25 16:01:02 -0500

It looks like you have provided a non-zero ambient value with the -av setting. This setting is used to specify background "ambient" illumination, which can be a useful shortcut if you need to run a fast simulation with few ambient bounces, but you have a good idea what the diffuse contribution to the scene should be. When a diffuse ray path reaches the number of bounces specified by -ab, it is assigned the value of -av rather than spawn new ambient rays into the scene.

Note: If your goal is physically based rendering, you should avoid the use of -av and instead use high -ab and -lr values (and a corresponding low -lw) in order to trace diffuse lighting paths farther into the scene.

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Thanks for the information on what -av does, and the information on -lr and -lw

Determinant's avatar Determinant  ( 2019-03-25 16:21:28 -0500 )edit

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Asked: 2019-03-22 14:59:47 -0500

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Last updated: Mar 25 '19