Shadow catchers with transparency in front of other shadow catchers crash Cycles X #92868

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Emily Cavalcante · 2021-11-06T00:35:43+01:00

Emily Cavalcante commented

2021-11-06 00:35:43 +01:00

System Information
Operating system: Windows 10
Graphics card: GTX 960 Driver 496.49

Blender Version
Broken: 3.0 beta e7e3431b29
Worked: sorry, no clue. tried builds from early last month and from before cycles-x was merged and they still crashed

Cycles will throw an error when rendering on GPU (Cuda and Optix) if there are shadow catchers with transparency in front of other (solid) shadow catchers. I think the error it threw was different on a scene I was working on, but it refused to render until I removed all objects (decals) with transparency marked as a shadow catcher.

The attached file errors for me both in viewport and rendering.
untitled.blend

**System Information** Operating system: Windows 10 Graphics card: GTX 960 Driver 496.49 **Blender Version** Broken: 3.0 beta e7e3431b2994 Worked: sorry, no clue. tried builds from early last month and from before cycles-x was merged and they still crashed Cycles will throw an error when rendering on GPU (Cuda and Optix) if there are shadow catchers with transparency in front of other (solid) shadow catchers. I think the error it threw was different on a scene I was working on, but it refused to render until I removed all objects (decals) with transparency marked as a shadow catcher. The attached file errors for me both in viewport and rendering. [untitled.blend](https://archive.blender.org/developer/F11739370/untitled.blend)

Emily Cavalcante commented

2021-11-06 00:35:43 +01:00

Added subscriber: @Drop

Brecht Van Lommel commented

2021-11-09 19:21:41 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Brecht Van Lommel commented

2021-11-09 19:26:26 +01:00

Added subscribers: @Sergey, @brecht

Brecht Van Lommel commented

2021-11-09 19:26:26 +01:00

This is a bit of a design issue, it's not clear we can support this easily without bigger changes. For 3.0 we may just disable transparency on shadow catchers.

The problem is that we do the shadow catcher split before evaluating the shader. For transparency to work we'd need to evaluate the shader first, then either continue with transparency, or split in the middle of the shade_surface kernel.

This is a bit of a design issue, it's not clear we can support this easily without bigger changes. For 3.0 we may just disable transparency on shadow catchers. The problem is that we do the shadow catcher split before evaluating the shader. For transparency to work we'd need to evaluate the shader first, then either continue with transparency, or split in the middle of the `shade_surface` kernel.

Sergey Sharybin commented

2021-11-10 15:03:21 +01:00

Think for 3.0 is easier to not allow a combination of shadow catcher and transparency. Not sure what should take priority (in terms, disable transparency on shadow catchers, or disable catcher on transparent objects). Feels like it should be uniform with how we deal with volume+shadow catcher.

The proper support we can look into for 3.1. Splitting in/after shade_surface kernel has advantage of avoiding duplicate work on shading same surface from 2 paths as well, but there was something tricky about it last time i've checked about implementing it.

Think for 3.0 is easier to not allow a combination of shadow catcher and transparency. Not sure what should take priority (in terms, disable transparency on shadow catchers, or disable catcher on transparent objects). Feels like it should be uniform with how we deal with volume+shadow catcher. The proper support we can look into for 3.1. Splitting in/after `shade_surface` kernel has advantage of avoiding duplicate work on shading same surface from 2 paths as well, but there was something tricky about it last time i've checked about implementing it.

Sergey Sharybin self-assigned this 2021-11-10 17:18:45 +01:00

blender-admin commented

2021-11-10 17:18:55 +01:00

This issue was referenced by blender/cycles@4c8e9da5b7

This issue was referenced by blender/cycles@4c8e9da5b725eba0eb0bb8e746d89d5f78c555f4

blender-admin commented

2021-11-10 17:18:55 +01:00

This issue was referenced by d26d3cfe19

This issue was referenced by d26d3cfe193793728cac77be9b44463a84a0f57e

Sergey Sharybin commented

2021-11-11 15:25:01 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Sergey Sharybin closed this issue

2021-11-11 15:25:01 +01:00

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Shadow catchers with transparency in front of other shadow catchers crash Cycles X #92868