Problem with vector blur and transparency

Hi guys,

I’m making an animation where there’s a flat plane, with a transparent png as the texture. This all works fine, however when I then add a vector blur node, the shape of the plane is noticable. Maybe not the best explaination, but I mean although the transparency still works, the transparent bit of the object, when moving fast, is slightly noticable, as if the texture is drawn onto a plate of glass.

I’ve googled it and things say transparency doesn’t work with vector blur, but I’m wondering if anyone knows any way around this?


You should be able to separate the transparent plane out of the Vector Blur pipeline by using a separate Render Layer for it.

The problem is that vector blur takes the entire object into account. To make it work, you could do a completely separate render pass first that only rendered the subject of the .PNG as white, and the rest of everything as black. Then, when you do your final render, you can bring that sequence of images back into the compositor and use them as a mask for the vector pass, dropping anything that should be transparent. You could do it all in one shot, but depending on how hot your compositor skills are, it is probably easier to just make a completely separate set of rendered files for the mask.