Lights with a size greater than zero visible in glossy passes even if glossy visibility is off. #116453

New Issue

Tyler Spicher · 2023-12-21T23:27:33+01:00

Tyler Spicher commented

2023-12-21 23:27:33 +01:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.33

Blender Version
Broken: version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: 9be62e85b727
Worked: 3.5. It also probably works in 3.6 but did not confirm.

Short description of error

When creating a light with any size greater than zero, that light will be visible in the glossy direct pass, and by extension, the combined output (although effect is very, very subtle) even when light's glossy visibility is off. There is a reduction in intensity but it is not fully gone. This is also tied to the intensity of the light. Making the light brighter will increase the brightness of the reflection, although it takes several doublings to make a significant difference.

This applies to area lights, point lights, and spot lights in my tests.

Disabling multiple importance sampling on the light "fixes" the issue, but then of course MIS has to be off. This may affect other render passes as well, like diffuse, but the effect is much more subtle.

I checked this is 3.5 and the behavior is not present. I am making somewhat of an assumption by thinking that this is due to the new way that lights are handled in 4.0. It feels like even though the "light" is not affecting glossy, the "object" that the light emits from is. See here:
https://projects.blender.org/blender/blender/pulls/108506
https://projects.blender.org/blender/blender/pulls/109329
https://projects.blender.org/blender/blender/issues/108505

Exact steps for others to reproduce the error
When opening attached Blend file and switching to rendered view (which is set to Glossy Direct) you will see there there is a reflection from a point light on the top of the monkey mesh even though the light's glossy visibility is set to off. Toggle off multiple importance sampling on the light to "fix" the issue.

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.33 **Blender Version** Broken: version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: `9be62e85b727` Worked: 3.5. It also probably works in 3.6 but did not confirm. **Short description of error** When creating a light with any size greater than zero, that light will be visible in the glossy direct pass, and by extension, the combined output (although effect is very, very subtle) even when light's glossy visibility is off. There **_is_** a reduction in intensity but it is not fully gone. This is also tied to the intensity of the light. Making the light brighter will increase the brightness of the reflection, although it takes several doublings to make a significant difference. This applies to area lights, point lights, and spot lights in my tests. Disabling multiple importance sampling on the light "fixes" the issue, but then of course MIS has to be off. This may affect other render passes as well, like diffuse, but the effect is much more subtle. I checked this is 3.5 and the behavior is not present. I am making somewhat of an assumption by thinking that this is due to the new way that lights are handled in 4.0. It feels like even though the "light" is not affecting glossy, the "object" that the light emits from is. See here: [https://projects.blender.org/blender/blender/pulls/108506](url) [https://projects.blender.org/blender/blender/pulls/109329](url) [https://projects.blender.org/blender/blender/issues/108505](url) ![image](/attachments/2f45d5a6-fd67-4517-883b-c4cd15c2ac36) **Exact steps for others to reproduce the error** When opening attached Blend file and switching to rendered view (which is set to Glossy Direct) you will see there there is a reflection from a point light on the top of the monkey mesh even though the light's glossy visibility is set to off. Toggle off multiple importance sampling on the light to "fix" the issue.

image.png

218 KiB

LightVisibilityIssue.blend

1.3 MiB

Tyler Spicher added the

labels 2023-12-21 23:27:34 +01:00

Pratik Borhade commented

2023-12-22 06:29:46 +01:00

Hi, thanks for the report. I don't think this is a bug. Diffuse light pass is contributing here due to slightly rough surface. In current setup, if you set roughness to zero or disable disable diffuse ray visibility, there won't be any ray in glossy direct pass that go to towards light source.
Forwarding to devs in case I misunderstood something.

Worked: 3.5. It also probably works in 3.6 but did not confirm.

Even 3.5 giving same results

Hi, thanks for the report. I don't think this is a bug. Diffuse light pass is contributing here due to slightly rough surface. In current setup, if you set roughness to zero or disable disable diffuse ray visibility, there won't be any ray in glossy direct pass that go to towards light source. Forwarding to devs in case I misunderstood something. > Worked: 3.5. It also probably works in 3.6 but did not confirm. Even 3.5 giving same results

👍 1

Pratik Borhade added

Module

Render & Cycles

Status

Needs Info from Developers

and removed

Status

Needs Triage

labels 2023-12-22 06:30:04 +01:00

Tyler Spicher commented

2023-12-22 15:07:21 +01:00

My apologies. You are correct it also occurs in 3.5 and therefore does not seem to be related to 4.0 lighting changes. Appreciate you catching that!

I may need to brush up a bit on how this works as I don't fully understand why roughness would cause it to appear. Thanks for forwarding!

My apologies. You are correct it also occurs in 3.5 and therefore does not seem to be related to 4.0 lighting changes. Appreciate you catching that! I may need to brush up a bit on how this works as I don't fully understand why roughness would cause it to appear. Thanks for forwarding!

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Lights with a size greater than zero visible in glossy passes even if glossy visibility is off. #116453