Velocity Blur seems to be supported by karma-xpu, but does not look at all like what the karma-cpu renders (whick look fine to me).
Here is a screen shot of the volume and its velocity trail:


The velocity is boosted for demonstration purposes:


This is the karma cpu render:


and here the karma-xpu render of the same thing:



I'm not sure if I'm doing anything wrong or if this is a limitation of xpu at this point.

I'm including a hip file in case anyone has a moment to look at it.

I'm using Houdini 20.0.547 on windows.

Hi. XPU's volume velocity blur implementation is somewhat different from CPU's. Due to performance considerations XPU does eulerian blur where field lookup points are modified by velocity, but this limits the blur to where velocity field exists. This is acceptable for pyro/smoke animations (which was our primary consideration), but the differences from CPU and field boundaries boundaries start becoming more apparent in cases like your set up where velocity scale is set to 100x.

Interesting. Thank you for the explanation, dlee.