The release notes for 19.0.423 suggest that light linking should be working on Karma XPU. The attached hip file has two boxes, the left with a glass pane. I have the light linker setup so the glass doesn't cast shadows with the lights. With the CPU, this renders as expected, but with XPU, it appears that none of the light gets past the glass.
Did I misunderstand the release note, or am I otherwise doing something wrong?
Thanks,
David
XPU Light Linking
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- d3zd3z
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- jsmack
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d3zd3z
The release notes for 19.0.423 suggest that light linking should be working on Karma XPU.
Perhaps the release notes meant that light linking, specifically, was working and did not include shadow linking.
Shadow linking does not appear to be implemented in XPU yet.
To let light through the glass, shadow linking isn't necessary. Using 'fake caustics' would achieve the effect of the glass allowing light through. Use the mtlx fake caustics node in line with the mtlx shader and the collect vop of the material x network.
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Unfortunately, it looks like this means there isn't any way to properly render this "donut under glass" with XPU. For my current scene, I've kind of worked around it by just disabling the glass entirely, as the object isn't that large in the scene.
It works without distortion using true caustics. It takes more samples to converge, but with XPU samples are cheap.
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Even with many times the number of samples, 1. it still seems pretty far from converging, and 2. the result is darker. I'm not sure where the darkness is coming from, this glass material should be letting all of the light through.
It probably won't converge easily with a small light source like that, but it does okay with a more diffuse env type light. The energy loss comes from the color limit, which defaults to 10. raising it to a million seemed to help, but there might be other energy losses still.
Ideally, refraction with with fake caustics will get fixed for XPU.
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- brians
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- brians
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Oh and to confirm
In XPU...
- LightLinking is working
- ShadowLinking is not working
https://www.sidefx.com/docs/houdini/solaris/karma_xpu.html#lighting [www.sidefx.com]
In XPU...
- LightLinking is working
- ShadowLinking is not working
https://www.sidefx.com/docs/houdini/solaris/karma_xpu.html#lighting [www.sidefx.com]
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- AnimGraphLab
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Just for someone figuring out how to actually link specific light to a specific geometry.
And to create a shadow link: hold Alt + LMB and drag the light in the middle (have a look at the link after last GIF).
You can also drag lights (from the right to the middle) to create a rule specifically for that light.
https://www.sidefx.com/docs/houdini/nodes/lop/lightlinker.html [www.sidefx.com]
And to create a shadow link: hold Alt + LMB and drag the light in the middle (have a look at the link after last GIF).
You can also drag lights (from the right to the middle) to create a rule specifically for that light.
https://www.sidefx.com/docs/houdini/nodes/lop/lightlinker.html [www.sidefx.com]
Edited by AnimGraphLab - April 7, 2023 09:59:28
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