Fix wrong conversion from power to radiance of area lights #109153

Weizhen Huang · 2023-06-20T11:48:15+02:00

Weizhen Huang commented

2023-06-20 11:48:15 +02:00

The correct conversion factor should be 1 / (pi * area), see #108505

Weizhen Huang added 2 commits 2023-06-20 11:48:28 +02:00

ae50bee223 Fix wrong conversion from power to radiance of area lights

The scaling should be `M_1_PI / area` instead of `0.25f / area`.
Ref: #108505

buildbot/vexp-code-patch-coordinator Build done. Details

15a4c7bea9 Move versioning code from `versioning_400` to `versioning_cycles`

Weizhen Huang commented

2023-06-20 11:48:52 +02:00

@blender-bot build

Weizhen Huang added the

labels 2023-06-20 11:59:36 +02:00

Weizhen Huang requested review from Brecht Van Lommel 2023-06-20 12:09:09 +02:00

Weizhen Huang requested review from Clément Foucault 2023-06-20 12:09:17 +02:00

Clément Foucault approved these changes 2023-06-20 14:10:34 +02:00

Weizhen Huang added 2 commits 2023-06-21 15:36:02 +02:00

9485654f96 Revert "Move versioning code from `versioning_400` to `versioning_cycles`"

This reverts commit 15a4c7bea9.

f3e97d7f74 Merge remote-tracking branch 'origin' into fix_area_light_scaling

Weizhen Huang added 1 commit 2023-06-26 11:59:35 +02:00

09c65b2484 Merge branch 'main' into fix_area_light_scaling

Brecht Van Lommel commented

2023-06-26 15:03:15 +02:00

For these forward compatibility breaking changes, I would prefer to do it for all lights at once. Also preferably all the units should be documented, and the mapping to USD units fixed along with this, also as an extra verification that we got it right. We can add more convenient units as additional options later.

Basically filling in a table like this:

	Normalized Unit	Unnormalized Unit	Conversion to USD
Sphere Light
Spot Light
Rectangular Area Light
Disk Area Light
Distant Light

For these forward compatibility breaking changes, I would prefer to do it for all lights at once. Also preferably all the units should be documented, and the mapping to USD units fixed along with this, also as an extra verification that we got it right. We can add more convenient units as additional options later. Basically filling in a table like this: | | Normalized Unit | Unnormalized Unit | Conversion to USD | |---|---|---|---| | Sphere Light | | | | | | Spot Light | | | | | | Rectangular Area Light | | | | | | Disk Area Light | | | | | | Distant Light | | | | |

Weizhen Huang commented

2023-06-26 15:41:59 +02:00

I do not quite get the point of the columns "normalized unit" and "unnormalized unit". What we are correcting here is the conversion factor between unit in the UI and the unit in Cycles. For the former, I think it is already documented and visible in the UI, W/m^2 for sun light and W for others. For the later it is always radiance ((Wm^{-2}sr^{-1})). Breaking changes in the conversion between these two only concerns area light.
But if you consider this conversion to USD (light->normalize) also as a breaking change, that would concern all the light sources, I can revert the conversion in #109329 and create a separate pull request for that. The conversion in #108996 would be there anyway if we change the sampling method, so I'm not sure.

I do not quite get the point of the columns "normalized unit" and "unnormalized unit". What we are correcting here is the conversion factor between unit in the UI and the unit in Cycles. For the former, I think it is already documented and visible in the UI, \(W/m^2\) for sun light and \(W\) for others. For the later it is always radiance (\(Wm^{-2}sr^{-1}\)). Breaking changes in the conversion between these two only concerns area light. But if you consider this conversion to USD (`light->normalize`) also as a breaking change, that would concern all the light sources, I can revert the conversion in #109329 and create a separate pull request for that. The conversion in #108996 would be there anyway if we change the sampling method, so I'm not sure.

Brecht Van Lommel referenced this pull request

2023-06-27 11:57:03 +02:00

Improve and clarify light units #109404

Brecht Van Lommel approved these changes 2023-07-03 13:34:03 +02:00

Brecht Van Lommel left a comment

I think this change is fine by itself, but let's wait with landing it together with other possibly compatibility breaking changes.

Brecht Van Lommel added 2 commits 2023-07-05 15:21:56 +02:00

5cfe1d687b Add forward compatibility for light energy changes

4f56515bb4 Merge branch 'main' into forward-compat

Brecht Van Lommel added 1 commit 2023-07-05 20:49:44 +02:00

41388ec510 Merge branch 'main' into forward-compat

Brecht Van Lommel commented

2023-07-06 19:01:58 +02:00

@weizhen you can commit this and other light changes now.

If needed, with the forward compatibility we can make further changes while keeping the .blend files load correctly in older Blender versions.

@weizhen you can commit this and other light changes now. If needed, with the forward compatibility we can make further changes while keeping the .blend files load correctly in older Blender versions.

Weizhen Huang added 2 commits 2023-07-07 17:02:29 +02:00

2478fa8f66 Merge branch 'main' into fix_area_light_scaling

8840001afc Change versioning number

Weizhen Huang merged commit 482211b7e0 into main

2023-07-07 17:03:09 +02:00

Weizhen Huang referenced this issue from a commit

2023-07-07 17:03:10 +02:00

Fix wrong conversion from power to radiance of area lights

Weizhen Huang deleted branch fix_area_light_scaling

2023-07-07 17:03:10 +02:00

Andras-Borsanyi referenced this issue from a commit

2023-07-12 17:32:37 +02:00