Geometry Nodes output attribute is not computed correctly #93572

Closed
opened 2021-12-02 15:14:52 +01:00 by Christopher Burns · 6 comments

System Information
Operating system: Ubuntu 20.04
Graphics card: 2080 ti

Blender Version
Broken: 3.0.0
Worked: ???

Exact steps for others to reproduce the error

In the attached blend file, the "foo" output should capture the original position attribute; instead, it captures the updated position attribute. If you re-arrange "pos" and "foo" in the Group Outputs panel, then "foo" correctly captures the input

geo-nodes-attribute-bug.blend

**System Information** Operating system: Ubuntu 20.04 Graphics card: 2080 ti **Blender Version** Broken: 3.0.0 Worked: ??? **Exact steps for others to reproduce the error** In the attached blend file, the "foo" output should capture the original position attribute; instead, it captures the updated position attribute. If you re-arrange "pos" and "foo" in the Group Outputs panel, then "foo" correctly captures the input [geo-nodes-attribute-bug.blend](https://archive.blender.org/developer/F12679767/geo-nodes-attribute-bug.blend)

Added subscriber: @christopher.burns

Added subscriber: @christopher.burns

Added subscriber: @null

Added subscriber: @null

This is the correct behaviour.

Untitled-1.png

Intercept the flow earlier with an "capture attribute" node to save the value.

The order of the output sockets also determines the order of flow execution. So if the thread with the "Add" node is at top then the value is modified before it is exposed again.

This is the correct behaviour. ![Untitled-1.png](https://archive.blender.org/developer/F12680316/Untitled-1.png) Intercept the flow earlier with an "capture attribute" node to save the value. The order of the output sockets also determines the order of flow execution. So if the thread with the "Add" node is at top then the value is modified before it is exposed again.
Member

Added subscriber: @HooglyBoogly

Added subscriber: @HooglyBoogly
Member

Thanks for the report. I think I get the problem in this case. I think we can make this situation work better-- all of the group outputs should be evaluated at the same time.

Thanks for the report. I think I get the problem in this case. I think we can make this situation work better-- all of the group outputs should be evaluated at the same time.
Member

Closed as duplicate of #93715

Closed as duplicate of #93715
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Reference: blender/blender#93572
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