While rendering motion blur with fast motion (cars) geometry begins vanish at random during rendering of a sequence.

[samjmason]

Hey all!

This is an error that seems to happen everytime I try and create a new shot. I'm using craft director studio to animate cars over a long distance. Geometry seems to vanish, or stop animating along the way. It's at random and different everytime I render. Sometimes a piece of the car vanishes or stops travelling. This is only with motion blur on. The gizmo remains but the geo vanishes. If I save and reopen the scene everything is back to normal until I render a few more frames. This feels like it has to do with memory and motion blur. Has anyone had this problem? It's happening in Vray 43002, also happens with the vray 5 beta. I've attached an image and a video to show the effect. I tried a few things. Changing scene to be meters (with rescale scene) I thought it might be an issue with embree and dealing with huge scene. But this didn't help. Has anyone encountered something like this?

ignore the compression errors in the gif. The thing to see is the black car losing a door and a tire stopping its travel.

Thanks!

[samjmason]

This link shows the problem a bit better. This is a continuous sequence with camera cuts. So it's happening in linear time. As you can see random geometry from the cars drops out. ALSO, I tried baking it down to regular transforms and removing the plugin, so I know it isn't craft director studio doing it.

[Morbid Angel]

Hey there. I've come across something like this before. First off, I think the reason things are disappearing is because of euler flip. Additionally, objects are probably not disappearing but rather their parent inherits an incorrect transform. The fact that they show in viewport but not during render solidifies that idea. If you enable subframe playback in your time slider options, you probably will see objects flipping etc. You can clearly see this on the wheels for example. They are not motion blurring correctly it seems. If you play the animation in viewport with subframe you may see that they either disconnect at subframe or flip or whatever.

With that said this is just a theory, and perhaps sharing a part of your scene which demonstrates the issues might help investigate further.