On shader changes, make sure these are uploaded in the cases where an expensive object rebuild isn't required #6

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Alex Fuller wants to merge 1 commits from boberfly/cycles:volume_shader into main

pull from: boberfly/cycles:volume_shader

merge into: blender:main

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Alex Fuller commented 2023-07-27 00:47:20 +02:00

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Hello,

In Gaffer we found that on shader updates to volumes, the volume itself would disappear unless we make sure to re-issue the volume and delete the old one. On further investigation I saw that we could use the same mechanism that other geometry types use: check need_update_rebuild (which I believe is triggered by tag_update calls) first, and then check is_modified() if the previous one fails (which can be triggered when used_shaders gets changed).

My hunch is that Blender normally keeps around the same ccl::Shader object pointer and only updates the shader graph so this was a non-issue, but in Gaffer we re-create the shader on every update, re-create and swap to the new shader. The above change I haven't tried in Blender yet, I'll do this next so it doesn't break things for Blender.

I've also snuck in this MR the get_precision() call for VDB loaders, as I found we need to check precision in an interactive render to determine if we need to re-issue a volume with a different precision.

Hello, In Gaffer we found that on shader updates to volumes, the volume itself would disappear unless we make sure to re-issue the volume and delete the old one. On further investigation I saw that we could use the same mechanism that other geometry types use: check `need_update_rebuild` (which I believe is triggered by `tag_update` calls) first, and then check `is_modified()` if the previous one fails (which can be triggered when `used_shaders` gets changed). My hunch is that Blender normally keeps around the same `ccl::Shader` object pointer and only updates the shader graph so this was a non-issue, but in Gaffer we re-create the shader on every update, re-create and swap to the new shader. The above change I haven't tried in Blender yet, I'll do this next so it doesn't break things for Blender. I've also snuck in this MR the `get_precision()` call for VDB loaders, as I found we need to check precision in an interactive render to determine if we need to re-issue a volume with a different precision.

Alex Fuller added 1 commit 2023-07-27 00:47:22 +02:00

70e100b94d On shader changes, make sure these are uploaded in the cases where an expensive object rebuild isn't required.

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Reference: blender/cycles#6

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