Posted-Date: Tue, 8 Dec 92 13:03:24 -0500
Date: Tue, 8 Dec 92 13:03:24 -0500
From: charlie@technosci.com (charlie fletcher)
Message-Id: <9212081803.AA00979@technosci.com>
To: rman@aero.org
Subject: Re: Shadowing and Lights...

 Mike Amirault writes:

1) How the heck do you do shadowing within a RIB file?  From reading the  
RenderMan
   Companion, it would seem as though your supposed to render the image  
*twice*,
   first creating a depth image and then using that to make a shadowmap. I have
   tried this with very little success.  I tried creating the depth image with
   a Display "test.tiff" "tiff" "rgbz" line and that seems to work but then I
   haven't been able to figure out how to use that image for the shadowing. I
   tried loading it in in a MakeShadowMap(?) call and then using ShadowSpot       
with that map but no dice...

	If this list ever gets a FAQ list, this has got to be #1. I wish I could help
	but I haven't been successful either (there is a rumor someone *has*
	done this.) It appears with my file that it is converted but then prman
	can't read the texture file. From my understanding you should declare
	your depth map of type "file" and give it a .z extension. (BTW-have you 

	been able to view this TIFF file?) If I figure out any more I'll let you know.

And,
2) Why don't light sources point in the right direction???  This is maddening.
   I have one light source in my scene, a SpotLight, and I'm trying to have
   it point from the origin (0, 0, 0) down a long hall, say (0, 0, 20). But,
   the light *always* appears to be coming from somewhere else, mostly the
   upper left.  I've tried declaring the light source before WorldBegin,
   after WorldBegin, before transforms, after... etc..

	I have been using 3DReality to set my lights and generally there is
	no problem with direction (once you account for the WorldScale
	factor.) I don't know your coordinate system, but (0,0,20) is up. Also
	remember that the (light, shape,etc) coordinate systems are left-handed.
	One guess might be that the default lighting is wiping out your light.
	Make sure these are off (or intensity zero) and render the scene. You
	shouldn't get anything. Now try adding your spot, checking to make sure
	all the parameters (cone angle, etc) are nonzero.

	Good luck (let me know what happens)
	Charlie