rendermask and moblur

[super gnu]

ive got a spinning propeller which i would like to render seperately and comp over my scene.. i thought rendermask would be an easy method.

however it renders the propeller as an ugly hard edged thing with no moblur.

in case it matters this is in RT gpu./

[super gnu]

actually ive tested it with another non-animated object in the scene, just fast moving camera, and there is no moblur applied to the edges of the mask in that case either.


related to this subject. id like to render my glass seperately as used to do for stills, to speed up rendering and allow tweaking after. but with heavy moblur in the scene im expecting comping issues. what is the best workflow to seperate/comp together motionblurred passes without issues?

note im just doing simple AFX comping, none of this cryptomatte enhanced nuke goodness unfortunately.

[vlado]

For the propeller, it would be best to render it either separately, or together with everything else; the render mask can't extract semi-transparent objects very well.

Other than that, separating motion-blurred objects would require making everything else matte, so that you only get the motion-blurred object.

Best regards,
Vlado

[super gnu]

i tried that too, with black background.. but when comping, i get a dark halo around prop.. if i do "remove black matte" in photoshop ( ive only tested still frame in photoshop so far) then i get a glowing halo round prop. i can kinda make it work by doing 2 copies, one with black matte removal and one without, then playing with transparency, but it never looks even close to the original, and much worse.

i assume there is a workflow that works, ive never been particularly into compositing.

[super gnu]

just to note those files were saved as 48bit pngs with premultiplied alpha.. dunno if it makes a difference.