Maniphest T93572

Geometry Nodes output attribute is not computed correctly
Closed, Duplicate
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Assigned To
None
Authored By
Christopher Burns (christopher.burns)
Dec 2 2021, 3:14 PM
Tags
  • BF Blender
  • Geometry Nodes
Subscribers
(null) McNull (McNull)
Christopher Burns (christopher.burns)
Hans Goudey (HooglyBoogly)

Description

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.blend778 KBDownload

Event Timeline

Christopher Burns (christopher.burns) created this task.Dec 2 2021, 3:14 PM
Christopher Burns (christopher.burns) added a project: Geometry Nodes.Dec 2 2021, 3:27 PM
(null) McNull (McNull) added a subscriber: (null) McNull (McNull).Dec 2 2021, 5:09 PM

This is the correct behaviour.

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.

Hans Goudey (HooglyBoogly) added a subscriber: Hans Goudey (HooglyBoogly).Dec 6 2021, 5:33 AM

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.

Hans Goudey (HooglyBoogly) closed this task as a duplicate of T93715: Geometry nodes attribute output depends on order of outputs.Dec 6 2021, 5:34 AM