Description

It seems that a Anim BP that generates a warning will break the updating of pins that are connected via fastpath in other parts of the graph. This was reported on the following UDN: [Link Removed]

See the attached video for more of the setup.

Steps to Reproduce
  1. Add a new bool variable to AnimInstance (or a custom derived class)
  2. Run the editor
  3. Create a anim BP
  4. Add a state machine with two states
  5. Add a transition that uses your native bool variable
  6. At the top level of the anim graph, connect the state machine to a blend node
  7. On the other input to the blend node add a blendspace (or some other form of blend) - see video for setup
  8. Connect the blendspace to a BP variable
    1. Check that the blendspace is using fast path
  9. Compile and manipulate in the animation editor
    1. Everything should behave as expected
  10. Kill the editor
  11. Delete the native bool variable
  12. Recompile & run the editor
  13. Back in the anim BP you should have a compiler warning in the Compiler Results
  14. Attempt to manipulate the input variable to the blendspace
    1. This will have no effect on the output of the blendspace
    2. Expected result: manipulating the input to the blendspace should change the output transforms as usual (despite the compiler warning)
  15. Connect the input to the blendspace to a node that just multiplies it by 1. This is to ensure that fastpath is no longer active
  16. Recompile the BP
    1. Notice now that when you change the input value to the blendspace, it behaves as expected.

Have Comments or More Details?

There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-115600 in the post.

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Fixed
ComponentUE - Anim - Runtime
Affects Versions4.26.2
Target Fix4.27
Fix Commit16416211
Main Commit16434427
Release Commit16416211
CreatedMay 13, 2021
ResolvedMay 24, 2021
UpdatedJun 1, 2021