Developer Notes

Grooms can get improper motion blur and artifacts when rendered with motion blur (vectors and or transforms) and Stencil Layers enabled and in some instances the groom disappears.

This issue is repeatable with the Meerkat Demo.


There is a problem with rendering Grooms bound and attached to animated skeletal meshes when the mesh belongs to a stencil layer in both the Deferred Renderer or the Path Tracer.

The groom does not render properly with lagging motion and low density.   In some cases, it appears that the groom disappears completely.

This issue can be recreated in the Meerkat Demo with the Meerkat following the steps to reproduce.

Steps to Reproduce
  1. Download and load the Meerkat Demo and open it
  2. Create an new level, add the amlMeerkat_BP blueprint to the level
  3. Create a new Level Sequence.
  4. Create a CineCameraActor and point it at the Meerkat
  5. Add the Meerkat and camera to the Level Sequence in Sequencer
  6. Assign one of the run or walk cycles as animation
  7. In the Layers panel, create a new Layer with the Meerkat assigned to it.
  8. Setup a MRQ render - be sure to enable Stencil Clip layers and add the Meerkat to a one of the Actor Layers.   Enable "Add Default Layer" and "Render Main Pass"
  9. Render
  10. Check the renders, the hair on the Meerkat is spotty and the motion blur is not correct.
  11. Go back into the MRQ Render Settings and remove the Stencil Actor Layers - disabling them.
  12. Re-render and compare to the original - there are not issues with the groom as there are when Stencil layers are enabled.

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ComponentUE - Anim - Sequencer - MRQ
Affects Versions5.15.25.3
Target Fix5.4
CreatedJan 31, 2023
ResolvedMay 9, 2024
UpdatedMay 15, 2024
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