I apologize if this has been dealt with in the past, but I am running into an issue where the flipbook generated by motion vector export and texture sheets produce completely different results.

Example 1: If I set an animation for 30 frames to go into a 1024x1024 with 8 images per line, what I get from motion vector output is a sheet of 128x128 textures, where the bottom half is just the final image repeated (since there is room for 64 frames). The same settings in Texture sheets produce a sheet with just the 32 images, stretched vertically (so 128x256). This makes the output unusable in Unreal

Example 2: Same as above with resolution of 1024x512 and a frame range of 32, to try and work with exact proportions. This produces expected results in Texture Sheets ROP, but the Motion Vector ROP just renders to the same 1024x1024 as above and then scales the resulting 64 frames vertically, resulting in 64 128x64 images. Also unusable.

Additionally to all this, the output vector image has good values in the G channel, but nothing in the R channel that is usable. So I get smooth motion along one axis of the image in the resulting material in unreal, but frame-y choppy animation in the other. Do the motion vectors require a particular render angle? Does it assume world space as opposed to camera space?

I'd greatly appreciate any help that anyone can offer here.

If you need 32 frames, why not render 36 and create a 6x6 texture sheet for both?

So I tried that, and it kind of illustrated the core issue even more. I set the frame range to 1-36, set the images per line to 6, and the result was the attached image. It didn't properly set the vertical height at all and still filled the frame with 64 images, with the last 36 just the same image repeated. Possibly this ROP node is just broken? It also continues to have the same issue of a Green channel with good values, and a red channel with nearly no information.

Can you share a screenshot of the parameters for the ROPs? I think you may be missing something in how you've set it up.

Rujuro! I'm so sorry. I've been replying without checking the node in Houdini. There does seem to be an issue with the frames it's producing. I'll have a look and get back to you.

Okay, should be fixed now. Seems a bunch of stuff internally had become disconnected. The latest change will be available in tomorrow's build of the Labs tools.

Oh good! Thanks for looking into it. I did send in my HIP file to support as well, just in case it helped, but that is good to hear.

I was diving in to see if I could figure out what was wrong (but I am still a relative newcomer to Houdini - so didn't make much progress there) and something that I find a bit maddening is the way nodes try and generate new connections and change connections every time you move them around. It leads to cases of connections getting changed unintentionally pretty frequently. Is there a way to toggle that behavior off? so that you have to explicitly join and cut connections?

UPDATE: I got the latest version on 4/11 and it DID fix the render button not working and corrected the frame output, however the vectors are still not usable, good values in the green channel, almost no info in red even though it is a fireball with expansion in all directions. It appears that a bug (#104345) has been logged with HIP file I submitted, hopefully this can be looked into as well?

Thanks again