Path: utzoo!utgpu!utfyzx!alias!pearce%alias
From: pearce%alias@csri.utoronto.ca (Andrew Pearce)
Newsgroups: comp.graphics
Subject: Re: Texture mapping by spatial position
Message-ID: <457@alias.UUCP>
Date: 14 Sep 89 19:25:24 GMT
References: <9119@pyr.gatech.EDU> <170@vsserv.scri.fsu.edu> <14266@netnews.upenn.edu>
Sender: pearce@alias.UUCP
Reply-To: pearce%alias@csri.utoronto.ca (Andrew Pearce)
Organization: Alias Research, Dammit
Lines: 41

In article <14266@netnews.upenn.edu> ranjit@grad1.cis.upenn.edu.UUCP (Ranjit Bhatnagar) writes:

   <stuff about solid texturing problems with animation and having to
    store a coordinate frame with each object/texture pair deleted>

|This almost solves the problem.  However, it doesn't handle the case of
|an object whose shape changes.  Consider a sphere that metamorphoses into
|a cube, or a human figure which walks, bends, and so on.  There's no way
|to keep the 3-d texture function consistent in such a case.
      .
      .
      .
|	2) define the base-shape of your object, and for each 
|	   metamorphosized shape, keep pointers to the original shape.
|	   Then, whenever a ray strikes a point on the surface of
|	   the metamorphed shape, find the corresponding point on the
|	   original shape and look up its properties (i.e. color,
|	   etc.) in the 3-d texture map.  [Note: I use ray-tracing 
|	   terminology but the same trick should be applicable to
|	   other techniques.]
      .
      .
      .
|If anyone actually implements these ideas, I'd like to hear from
|you (and get credit, heh heh, if I thought of it first).  I doubt
|that I will have the opportunity to try it.

	I believe this is very similar to what Witkin and Terzopoulos did at
Schlumberger around 1987. I can't for the life of me find the paper though.
I did see a film at CHI+GI 87 (and a SIGGRAPH too) where they drove a cone
into a solid textured cube. The cone caused the cube and texture to deform
non-linearly. They also moved the coordinate frame of the texture without
moving the object causing the texture to appear to flow around the cone.

	Can someone mail me the reference to the paper, if there was one.

- Andrew Pearce
- Alias Research Inc., Toronto, Ontario, Canada.
- pearce%alias@csri.utoronto.ca   |   pearce@alias.UUCP
- ...{allegra,ihnp4,watmath!utai}!utcsri!alias!pearce