Fix crash reading RenderSettings with empty arnold:filter on a RenderVar (#2677)

[cpichard]

Summary

Fixes a crash (segfault) when reading a UsdRenderSettings scene where a RenderVar has an empty arnold:filter attribute (custom string arnold:filter = "").

The empty string overrode the box_filter default with an empty filter type, so CreateArnoldNode("") returned nullptr and the node was then dereferenced via AiNodeGetNodeEntry(filter) in libs/common/rendersettings_utils.cpp, crashing Arnold. This is shared code, so it affected both the usd procedural (kick) and the render delegate / husk paths.

Fixes #2677.

Changes

• libs/common/rendersettings_utils.cpp:
  • Only override the default filter type when a non-empty arnold:filter value is authored.
  • Skip the RenderVar if the filter node could not be created (unknown/invalid filter type), instead of dereferencing a null node.
• testsuite/test_2677/: reproduces the crash (scene reduced from a customer file).

Test

testsuite/test_2677 renders the repro scene via kick; it crashed before the fix and renders after it.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes a crash in the shared RenderSettings translation path when a UsdRenderVar authors an empty arnold:filter (or otherwise results in a filter node that cannot be created), preventing null dereferences during AOV filter setup. This impacts both the usd procedural (kick) and render delegate / husk paths.

Changes:

• Treat an authored empty arnold:filter as “not overriding” the default filter type (box_filter).
• Guard against invalid/unknown filter types by skipping the RenderVar if filter creation still returns nullptr.
• Add regression coverage via a new testsuite repro scene for issue #2677.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
libs/common/rendersettings_utils.cpp	Adds defensive handling for empty/invalid arnold:filter values to avoid null dereference crashes when configuring AOV filters.
testsuite/test_2677/README	Documents the crash repro and test parameters for running the new regression test.
testsuite/test_2677/data/test.usda	Provides a minimal USD scene that previously triggered the segfault (empty arnold:filter).

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