CGTalk - Rendering shadows

krumme

11-02-2008, 12:09 PM

Hey, I,m trying to render out an object with a raytraced shadow (mental ray) for compositing.
I,m placing the object on a plane with a use background shader but after rendering out with alpha and opening in photoshop the shadow seems to be surounded by a white area (the environment background color I take it). How can i render out with just the object and soft shadow please.
thanks.

wesdood

11-03-2008, 12:00 AM

render it in layers.

make the shadow pass a separate render.

krumme

11-03-2008, 03:45 AM

Thanks I sorted it, had to change the reflection limit on the use background shader to 0, Usebackground shader still giving me grief though.

mwgriffin

11-21-2008, 10:30 PM

yeah dude. I've tried to use the background shader to capture shadows as autodesk has instructed, but it simply doesn't work... until now. I figured out what I was doing wrong... For the alpha channel to work, you have to not only turn the reflection down to zero, but you also have to turn the reflection limit down to zero. Then it will work. But that method of using a background shader to capture shadows is not as easy as using the shadow pass in maya 2009, but of course that functionallity has a bug in it, so it's back to using background shaders until they fix it.

Sybexmed

09-30-2009, 04:21 AM

Has it been fixed? I havnt tried to render a shadow pass but i need to very soon.

yeah dude. I've tried to use the background shader to capture shadows as autodesk has instructed, but it simply doesn't work... until now. I figured out what I was doing wrong... For the alpha channel to work, you have to not only turn the reflection down to zero, but you also have to turn the reflection limit down to zero. Then it will work. But that method of using a background shader to capture shadows is not as easy as using the shadow pass in maya 2009, but of course that functionallity has a bug in it, so it's back to using background shaders until they fix it.