View Full Version : Mental Ray - subD question

03 March 2004, 09:46 PM
I know Mental Ray doesn't support partial creases on subDs. But isn't it supposed to do the ones with full creased edges!?

I would very much appreciate any suggestions on how to get MR to render full creased subDs...


By the way, does anybody know why it's like that with subDs at all? And will there be a time, when one would possibly be able to adjust the amount of crease continuously?

06 June 2004, 04:48 PM
aargh! yes, this really, really sucks.

could't find anything in the manual regarding this pretty fundamental limitation of MR rendering (which works like a breeze out of XSI, btw).

i'll do some research and post back here if i find something.

06 June 2004, 09:35 PM
ok, i found a workaround. i hope the attached pix gets through. here's the theory:

you have a piece of poly that you'd like to subd while keeping a bunch of full crease edges. they usually DON'T render in mray.

what you can do is, extract and separate all the faces within a boundary of edges that are supposed to be full crease, so you end up with a poly object for each one of your groups of faces.

now convert these separate poly objects into subds, and they will meet with nicely creased edges - and these will render in mray like a breeze.

06 June 2004, 11:39 PM
preforming a collapse on the sub-d object will also allow mental ray to render creases. But of course this deletes the sub-d hierarchy.

06 June 2004, 12:43 AM
Mental Ray will render full creases on Subds at level 1 and higher. It won't render them on Level 0. I just tested this on 6.0, not sure if it's the same in 5.0.

06 June 2004, 11:03 AM
I will never use H-SubDivisions, just manually crease on the cage mesh by putting edges close together and using 0-level smoothing (Polygon Smooth). Alias's efforts to make H-SubD's useful has failed.

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