Mass crowd ISKM instances intersect uneven terrain

Development Programming & Scripting
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1

Instanced crowd members can walk through rounded or uneven terrain because their Mass paths use straight segments that do not follow the surface closely. High-resolution actors are corrected by Mover, but instances may still be close enough for the clipping to be visible. Most importantly, the subsequent correction can also cause a noticeable pop when switching to the actor representation.

  1. What is the recommended solution for non-flat landscapes? Should we add ground projection for instances, adjust native Mass or NavMesh settings, or use another supported workflow that preserves seamless representation transitions?
  2. In case there is a way to greatly improve this for the ISKM entities, is Mover for high res actors still recommended/needed?

Best regards,

Matthias

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Steps to Reproduce

  1. Open the MetaHuman Crowd Sample in Unreal Engine 5.8
  2. Open MAP_Plaza
  3. Add a rounded ramp to an area traversed by the crowd (as depicted in the screenshots)
  4. Ensure the ramp is covered by the NavMesh and rebuild navigation (we also made sure there is no nav mesh under the ramp, but it didn’t change the result)
  5. Run the map and observe crowd members using the instanced representation rather than high-resolution actors
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3

Hello!

Apologies for the delay. I am getting up to speed with this sample. I do see the issue you are seeing with a curve ramp, but I am not sure what may be causing it. My initial thought is that something with either the NavigationHeightSmoothingProcessor is being overridden or stomped, or it might be an issue with how the path corridors are built with a flat Z between them rather than one that follows the curve. I will try to reach out to some of the team that worked on the sample to see if it is something they encountered or have other ideas.

-James

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4

Thank you for your patience! So there is an issue with how the navigation corridors are being used to smooth the Z height over time, but it isn’t the smoothing that is an issue but using the center of the corridor which is not necessarily on the navmesh surface. The likely fix is implementing a processor to periodically sweep for agents that are moving against the geometry. This would allow them to find their proper feet location and prevent most clipping. I noticed using a landscape that there are times the entities would fully walk through the hillside with the whole mesh being under the landscape. I set up some basic sweeping in a processor that seems to be running with okay performance, but depending on numbers needing to be done and complexity of your physics scene, this could be more expensive.

As for if you should keep using Mover, the answer there is emphatically yes. It is what we used for The Witcher 4 demo last year and where we have been continuing to put development efforts.

-James

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5

no worries, thanks for looking into it!

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