problem with motion blur on sliceplane animated objects

[UBIKmh]

Max crashes after a few frame and after a several Vray warnings like "cannot MB on object with changing topology".
Vray 1.5
Anybody have an idea on how to bypass this? Or, better, fix this. Is this a known problem?

Please advice.

Marc

[joconnell]

The reason is that Vray doesn't like polygons appearing and disappearing between frames as it uses vertex information to create it's motion blur directions. You can try lowering the duration of the motion blur to less than 1 and also try changing the interval centre to 0.

[UBIKmh]

Duration is allready < 1. I have a Physical Camera with a shutterspeed of 1/50. Will try to set the interval center to 0, which makes sense to me when Vray doesnn't like polygons changes in between frames.
Thanks for the tips.

[Neilg]

With animated slices you need to subdivide the mesh first and check on 'operate on (the triangle one)' within the slice modifier.
Had the same problem a while ago, someone on here told me that

[UBIKmh]

Well, it looks like it's not crashing anymore (fingers crossed, we're trying it out on a simple file with simple boxes not on a whole soccer stadium), but when Vray gives the topology warning it doesn't do any motion blur. Every X frames that happens, depending in the subdivision of the object. A box with 1-1-1 has the least problems. The easiest option would be to do all the morionbur in after effects, but I'm not sure that will look good. No experience with that.

[Neilg]

http://www.revisionfx.com/products/rsmb/

This usually did a good job when we didnt have time. far better than any other post mb i've seen.

[UBIKmh]

OK, just bought it and I must say, it does a wonderfull job. I think this could be the saviour of the day. Thanks Cubiclegangster.