I render an animation with EEVEE and every frame takes less than 10 seconds to be rendered (in 4K). I also output normals, AO, and other images in the same render (using a File Output node). Unfortunately I also need a position map (P-map) and a velocity map of the same render. I would like to have it in the same render, but also having an additional (fast) render only for these it's fine. For the position map, I found that I can have it by using a special emission material with a position information as input. As for the velocity map, it seems that EEVEE is not able to output velocity maps (?).

My first attempt was creating a new scene, linking all objects from the first (main) scene and using Cycles in this new rendering, with a material override for the P-Map and with a velocity pass that outputs the velocity I need. The only problem is that since I am using Cycles (although only to receive information, not for actually render), a single frame takes no less than 30 seconds. Is there a smarter way to receive these data?

  • $\begingroup$ Do you need correct velocity pass on deformed geometry? $\endgroup$ – Jaroslav Jerryno Novotny Jan 14 '19 at 11:50
  • $\begingroup$ @JaroslavJerrynoNovotny I do not know (and I am also not sure about the meaning of "deformed geometry"): it has been requested for compositing (using Nuke) $\endgroup$ – MadMage Jan 14 '19 at 12:59
  • $\begingroup$ Deformed geometry would be characters, non-deformed would be solid objects. I asked because for solids you can adapt this: blender.stackexchange.com/questions/29007/… to output not the magnitude but the velocity vector itself and drive an emission shader with it. For handling rotation or mesh deformation there would be more scripting and it would have to be done on per vertex basis, baked into vertex colors animation and used in shader. $\endgroup$ – Jaroslav Jerryno Novotny Jan 14 '19 at 13:17
  • $\begingroup$ You can also output some geometry pattern on your meshes and in Nuke get the motion vectors from optical flow. $\endgroup$ – Jaroslav Jerryno Novotny Jan 14 '19 at 13:29

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