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Luke Fraser

InstanceFile Geomtry Motion Blur

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I recently built a animating instance geometry system. The instancefile attribute is used to select between different files. There is subframe instancefile selection information as well and the feature for subframe motion bur is enabled on the SOP. I am unable to achieve motion blur with this setup.

I was under the impression that if Mantra received subframe information of the same geometry(same number of vertices and points, with the same numbers and attributes) it would be able to compute the motion blur. 

At the current state I don't have velocities attribute associated with the loaded geometry. This is an undesired way to achieve motion blur. 

Any help would be appreciated. I can post a .HIP file when I simplify the method down to a few nodes.

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I was under the impression that if Mantra received subframe information of the same geometry(same number of vertices and points, with the same numbers and attributes) it would be able to compute the motion blur. 

 

 

This is generally true, but the instancefile is used by the Fast Point Instancing procedural and doesn't take multiple copys of the geometry for motion blur. Usually you'd either put a velocity on your instance geometry if you can get away with velocity blur or you really need true deformation blur you need to load the geometry into Houdini and use Full Point Instancing with the "instance" attribute pointing to you're geometry nodes to instance. You might be able to use packed disk primitives with the second option, to avoid having giant ifd files, but I haven't tried it yet and I'm not completley sure how they handle deformation motion blur.

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Have you tried to calculate the velocities with the trail SOP set to "Compute velocity"?

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