Path: utzoo!utgpu!news-server.csri.toronto.edu!dgp.toronto.edu!andreww
Newsgroups: comp.graphics
From: andreww@dgp.toronto.edu (Andrew Chung How Woo)
Subject: Image processing question
Message-ID: <1991Apr2.181356.4537@jarvis.csri.toronto.edu>
Organization: CSRI, University of Toronto
Date: 2 Apr 91 23:13:57 GMT
Lines: 26

I am looking for ideas, algorithms, or references on the following problem:

INPUT: 	(1) raster background (24-bit per pixel)
	(2) 3d geometry
	(3) one-bit raster boundary defining a region of the raster
	    background representing a forground object (we want this object
	    to appear in front of the rendered geometry in the final image)

GOAL: Composited, anti-aliased image in which the part of the raster
	background defined by the one-bit raster boundary appears to be
	in front of the rendered geometry.

THE PROBLEM: I know how to generate the one-bit forground raster region,
	and know how to do anti-aliased compositing given 8-bit mattes
	approximating coverage information for the rendered geometry and the
	forground raster object.  BUT how can I generate or approximate
	8-bit coverage information for the forground raster object given only
	the background and 1-bit boundary information?

It seems that some active edge detection is required here, but such detection
tends to be expensive and is bound to fail when shadows are involved.  Any
suggestions or thoughts, please e-mail me at andreww@dgp.toronto.edu.  

Thank you very much for your time.

Andrew Woo