geometry samples in physical camera?

[sharktacos]

Motion blur in the render settings has "geometry samples" which are important when doing MB on things like rotating propellers. The physical camera does not have this option for motion blur. How is this controlled in a physical camera, and what is the value it uses by default?

[ivaylo.ivanov]

The geometry samples have nothing to do with the physical camera. The Render settings option is the only one.

[sharktacos]

Okay so the duration and interval center settings are overridden by the MB settings in the physical camera, but geo samples is still respected. Am I correct that the bias, shutter efficiency, and prepass samples are also respected with the physical camera?

[ivaylo.ivanov]

The physical camera overrides camera related mb parameters. The prepass samples are also global since they affect the geometry.

[sharktacos]

Okay, I think I mostly got it. Here's a breakdown of what I'm understanding. Can you tell me how bias works in the physical cam (in red below)?

overridden by physical camera:
duration default: 1
Same as shutter angle of 180 for "movie camera"
interval center default 0.5 (blur appears between frames)
Physical cam is always 0 (blur appears at exact frame position)
bias: 0
is this controlled by "center bias" in the physical camera?

set in globals (independent of physical cam):
shutter efficiency
prepass samples
geometry samples

[VISUALMAN_TOKYO]

Shutter angle of 180 degrees equals duration 0.5.
Center bias in physical camera is used for the look of the bokeh (brighter or darker in the center or the edges), bias in render settings is used to control biased motion towards the beginning of the exposure interval (negative) or towards the end (positive), bias 0 will distribute the motion evenly. Values different than 0 can be mostly used for stylized motion blur such as comics style motion blur, etc., but if you are looking for a more realistic motion blur you should go with bias 0.

[ivaylo.ivanov]

Yes the center bias is for the DOF, this bias setting is controlled by the physical camera and you can't change it.

[sharktacos]

"Shutter angle of 180 degrees equals duration 0.5"

So the render settings default to the equivalent of a 360 degree shutter? ... wow, that's surprising. Thanks for the correction.
Sounds like the best bet is to use physical camera for MB then.