Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!icdoc!ra2
From: ra2@doc.ic.ac.uk (Roger Attrill)
Newsgroups: comp.graphics
Subject: Re: Texture mapping onto 3-D objects
Message-ID: <2674@gould.doc.ic.ac.uk>
Date: 19 Dec 90 22:00:53 GMT
References: <1737@winnie.fit.edu>
Sender: news@doc.ic.ac.uk
Organization: Dept. of Computing, Imperial College, London, UK.
Lines: 47

In article <1737@winnie.fit.edu> rao@sun9.cs.fit.edu (Rao Ranjan /ADVISOR-Shoaff) writes:
>Hi netters,
>
>Could anybody provide me some information about texture
>mapping. I would like to know, if there is any
>algorithms for mapping 2-D polygonal textures ( random ) on to 3-D objects
>( for example 3-D solids which have curved surfaces) available. Is
>there any software packages available in the market that do this ?
>Currently I am working on my thesis in the field of computational
>Visualization. 
>

Yes. I've written a machine code version of RayShade V3.00. (Yes I'm crazy!).
I've incorporated this feature (along with others) into the program, and it
works a treat. There is a problem in that seeing as the 2D texture (a logo
for instance) *is* 2D, then the person creating the scenefile has to do most
of the positioning work, - scaling,rotating etc. I've initiated 2D textures
to have unit size in +x and +z directions with bottom left of the picture
at the origin. The normal points in the -y direction. The texture is then
mapped *through* an object - not *around* an object. This means it is best
suited to mapping to flat surfaced objects. However, nice effects are achieved
when mapping a face onto a distorted sphere.  If you get the source code
to Craig Kolbs' RayShade, then this is an excellent example of how to map
many different types of textures. It's not hard to add one more, and add
a routine to compute the RGB values at a given point on your 2D image, in
order to map it onto an objects' surface at the hitpoint.
 If anyone has a method of wrapping an image *around* an object, I'd be
most interested. I'd imagine this would imply some intensive computation
and would not be globally useful. Would different algorithms be needed for
each primitive type. eg for cones *and* superquadrics!!! God forbid! What
about mapping pictures of farms and cows onto fractal landscapes. Maybe
even some people skiing down snowy mountaintops. Shadows might be hard
though!!

Time to abort!

 Merry Xmas

     Rog.

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|   Roger C. Attrill   | I don't always think therefore I'm not necessarily. |
|   ra2@doc.ic.ac.uk   | I couldn't have done better unless I did it myself. |
|   Imperial College   |          and other variations on a theme.           |
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