Motion Blur rotation shrinking objects?

[PHM]

We're working on a car animation, and when motion blur is turned on in camera settings, rotating objects (like the car wheels) shrink.
The more blur, the more they shrink.
Anybody had the same problem or know a workaround?
Tried fiddling with lots of motion blur settings, but it just changes the amount they shrink by.
A similar thing came up in the lightwave forum, but there aren't similar settings for C4D

viewtopic.php?f=36&t=43280

[PHM]

Should probably add more detail - sorry, can't post pics as under non-disclosure.

The wheels have Octane object tags on - tried using transform and transform/vertex
Using Octane Camera tag motion blur - thinlens, the bigger the shutter setting, the more the things shrink. Changing caching frames settings can also make the shrinking more/less

[aoktar]

Try higher time steps on render settings. It's expected result when matrices have rotation differences more than 90 degrees between two frames

[PHM]

Hi Aoktar, thanks for the reply. Do you mean Time Sampling Per Frames in the main render settings menu?
Strange things happen if I change that, although the wheels are the right size. Sometimes the blur will be correct, sometimes no blur, sometimes the whole frame will be blurred if things are mobing or not.
It goes from 0-32, what is the effect of the change?

[aoktar]

see image. It divides the frames to value and produces more keyframes for renderer. Can you put a scene to show what you mean?

[PHM]

Sure, this is with Time Sampling 1, the wheels are blurred but they shrink

mblur1.JPG (25.25 KiB) Viewed 4301 times

This is with Time Sampling 2 (or more)
The wheels are the right size, but either not blurred, or everything blurs - seems to happen for a few frames, then switch...

[aoktar]

Sorry but i mean scene not images. It doesn't make any sense for a programmer. We divide the scene until find the problems.

[punchin]

I am having exactly the same issue.
Mblur time samplings per frame up to 5.. lovely round wheels on a fast moving car. Then all of a sudden.. bang 1 fame crazy Mblur then NO Mblur.

[punchin]

problem solved.. it was a keyframe problem using the function ( track after - continue after)..