Slice modifier+Motion Blur

[demetrio]

Hello, while animating a couple of slice modifiers to have a building being sliced in different phases (structure+slabs+mullions+glass) I got into trouble with motion blur, and the vray log was complaining about geometry changing from frame to frame, meaning that I couldn't get proper motion blur.

Do we have to animate building growths with masks in compositing afterwards, or using a multipass moblur approach? Is this the only way to go? It would be a shame, because in faster moving cameras motion blur works great, and doing it in post is impossible because the velocity channel gets all messed up with the slices as well.

If any of you guys have a workaround for this it would be perfect, I'm trying to convince people in my company to use motion blur more often because it works really well, but with this drawback it's gonna be pretty much impossible :P

Thanks in advance to all,
D.

[tammo]

Animated slice is making a new mesh at every frame like an animated boolean.
Even the amount of polygons is changing, so it is not possible to get 3D motionblur.

[Neilg]

Subdivide all the meshes that are being sliced and switch slice mode to operate on faces.

[chipnuts]

I know this is an older thread (and also understand why motion blur + slice isn't 'ideal'), but I'm getting a crash when doing this with Vray 3 BF/BF + slice (on faces) + motion blur. Sent log and screen shot to support.

[svetlozar.draganov]

Have you tried to use Vray Clipper instead of Slice Modifier?
http://docs.chaosgroup.com/display/VRAY3/VRayClipper

[vlado]

We cannot fix the issue with the slice modifier. As Svetlozar suggested, the VRayClipper may work.

Best regards,
Vlado

[chipnuts]

The problem with Vray Clipper is, it's Vray specific. We have been known to use other renderers from time to time. I've gotten it a bit more reproducible in that when rendering from a non-camera view (whether it's orthographic or Persp), it crashes to desktop. I'll keep working with support to at least supply some scenes/objects that break.

[vlado]

I can't help you with other renderers I'm afraid - I can only offer a solution for V-Ray. The original problem with the Slice modifier (getting proper motion blur from an animated mesh and/or Slice modifier) is not fixable (in any renderer).

We will fix the crash for sure, but you will probably still not get the effect you are after.

Best regards,
Vlado

[chipnuts]

Agreed. Yeah, I understand it's not an ideal situation for any renderer, but I wouldn't expect it to do a hard crash. (Submitted file to FTP and repro steps via email.) The renderer should at least 'try' to figure it out by giving me a blurry mess. Also, it doesn't crash on every frame as the slice happens, but does crash on the same frames every time.

It just never fails for us when we create a scene using very specific things like vray clipper, that we'd end up having to give the file to the client who doesn't have vray, so then we have to explain why it's not showing the slicing for them like it did in the render.

[vlado]

Also, it doesn't crash on every frame as the slice happens, but does crash on the same frames every time.

If you can get us some example scenes, we will fix the crash.

Best regards,
Vlado

[chipnuts]

Yep, Tsvetan in support is on it! Thanks, Vlado!