this problem has always been there, this is not an Octane bug,
this is a limitation of the Maya plugin which is missing MB time sub-sampling for geometry :
This problem is obvious when using the
symmetric MB direction,(but also happens with
after and before for objects with fast non-linear movement).Currently in the plugin, for Motion-blur geometry is only sampled 2 times (= only 1 MB step per frame):
for
symmetric shutter alignment, geometry is sampled once before and once after the current time,so with only 2 samples the geometry at current time is interpolated between the pre-sample and the post-sample.
This is why it shrinks with rotation,
symmetric must only be used with at least 3 samples ( = 2 MB steps ),else with only 2 samples we have this:
- from geometry pre-sample to geometry post-sample, vertex interpolation at current time give a shrinked object (red).
WORKAROUND
The workaround for this problem is to set your scene at a higher frame-rate for example change from 25 FPS to 250 FPS,
then export animated scene ORBX, in Standalone set the framerate to 25 FPS and that's it:
you can now render the ORBX in Standalone with perfect 10 steps motion-blur.