Tuesday, September 04, 2007

Shave and Haircut: Shadows (Mental Ray Buffer)

Ok probably the most important thing I've learned over time is about Shave shadows. Much of this is probably really obvious...but here's a quick rundown for Shave and Haircut Shadows using the buffer:

Geo Shadow - The geometry that the hair is attached to is casting shadows on the hair if this feature is turned all the way up. For some reason for quite some time I always thought this attribute affected how the hair casted shadow on to the geo under it...I was very wrong. So if you want to create a rim light pass for the fur, you would want to put a light behind your geo and hair and turn geo shadow all the way up.

Self Shadow - Hairs casting shadows upon themselves, that one is pretty straight forward.

How to avoid a major flickering problem when rendering with the buffer - If your throw a light into the scene (without properly setting up the shave shadow attributes) and animate the hair moving around you are most likely going to get a flicker/jitter/shimmer render. I've typically been working with a spot light as my key light. After creating my light with a scene that already has hair, I select the light then go to the shave menu ->Shadow -> Add selected lights. This will create a new attribute in your spot light. If you enter 1500 into the resolution and 30 into fuzz this will give you a good starting point to avoid those flickers. Joe Alter suggested those numbers himself and they've been working great for me.


Michael said...

Man, this post just solved one of my biggest Shave issues. Great tip!

wabash said...

no prob. i'm now using mental ray hair primitives and its soooo much faster and looks great. Only a few things to figure out there. I've also posted on that as well. If you use mental ray I would highly recommend using it.

Anonymous said...

Hi am newbie using shave and hair..wanted to know as to how do you get shave and hair shadow as a seperate PASS on the body, which can be composited as per requirements.

Waiting for reply


wabash said...

You know I have attempted to do a separate hair shadow pass myself using shave...but I haven't found a good system. I've tried using the use background shader and turning the primary visibility of the hair off...but no luck, if you happen to find this info out...please do let me know.

Sorry, will let you know if I find this out.

DommyBoy said...

Hey mate, I too use Primitive mode, but again like other posts here.. have no clue how to comp out a shadow pass and a colour pass. If you figure it out.. do let us know!

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