Multi segement motion blur with particles

Was trying to find a clean solution to rendering particles with multi segment motion blur, found a way that is quite quick...

A bunch of points are created at 0,0,0. The number of points is equal to the largest ID at the end of the particle sim.

A VOP SOP loops through the particle sim and tries to find a particle with the same ID as the current point number. The position is copied onto the point, and a matchedPt attribute is created that stores the point number of the particle in the sim. This is so that the point() expression can be used later to copy attributes from the sim.

The point count is constant so deformation blur will work with this setup. The alpha is set to hide the points when the particle dies and before it is born, with 1 frame buffer at either end of the particles life so that you don't see it streaking back to 0,0,0. That could be set to a 1 frame / oversamples buffer, I just haven't tried that yet...

Oversampling of the popnet is 30 and geo time samples is 5 for the render. I wish popnets would interpolate between oversamples .... cache node might do it but I don't think so...

hipnc is here - created with build 10.0.346

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I, Houdini

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