VAT Animation — Velocity Only Works with “Time” Node

Development Rendering
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1

Noticed an issue with Vertex Animation Textures (VAT): velocity data only generates correctly when the material is driven directly by the “Time” node. If I use a scalar parameter or a Material Parameter Collection to drive animation instead, velocity stops working completely — both in render and at runtime.

Video attached shows the difference:

  • driven by Time node → velocity works :white_check_mark:

  • driven by scalar/MPC → no velocity :cross_mark:

Seems like VAT velocity output only updates when tied to the built-in Time expression. Can anyone confirm if this is a known limitation or a bug?

2

This is working as intended. If you need a velocity without time, you will need to use the “Previous Frame Switch” node provided with both the current and prior frame WPO value.