Yea, I definitely need a better example for the imposter motion vectors.
Honestly that feature is still a bit early and I have only done one test with it, and the quality was so-so. That is because in the version checked in, its just doing linear blend using the X and Y axis, but not the diagonal axis. I have messed around with a new version and the quality is all about the blend weighting. Solving that problem was a bit trickier than I had thought as you need to write a shader kind of like the 2d anim blend spaces, it needs to pick the closest 3 neighbors and weight between them using a triangular layout, since the camera can move diagonally not just updown and leftright.
I have some experiments for the blend weights I can post later.
And yes, the imposter function is a mess. I have also started redoing it using octahedron layouts and the next version will be much cleaner and the angles will be evenly distributed. There is just the question of what to do with the empty corner space for when you don’t care about frames below the horizon.
Are you able to render out the motion vectors out of houdini? That is the most important part.
Are those clouds lit in houdini or UE4? If they are lit in UE4 you could try interpolating between normals and alpha only, which I have found in many cases to be more effective than motion vectors. If they are in houndini that idea may not work as well.
I set up something similar in VUE for baking couds from all angles (just around Z though) and it was a pain in that program. I am betting houdini is a bit better about that.
btw imposters go great with ray tracing. If you perform the trace by average the entry and exit positions between the weighted nearest frames you can get virtually seamless frames (no examples at the ready sadly but I have tried it).
Cheers.