Path: chuka.playstation.co.uk!news
From: Harvey Cotton <hc054@mdx.ac.uk>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Environment Mapping
Date: Mon, 29 Mar 1999 18:20:05 +0100
Organization: PlayStation Net Yaroze (SCEE)
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References: <36FCF4E8.63C0@mdx.ac.uk> <7dlhjs$7a21@scea> <36FE86BD.6FE0@mdx.ac.uk> <36FF4A6B.93A706E9@hinge.mistral.co.uk>
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> I don't know of any game that does true environment mapping (as it takes
> ages
> to calculate). However, I did post some code ages ago that would do 1 or
> 2
> axis mapping single texture mapping for a TMD model made up of textured
> gourard poly3's
> - all it would take to make it work as an overlay would be a second copy
> of the
> object (sharing the same normal and vertex segments as the mapping
> overlay) to be
> sorted first. I seem to remember that someone else also posted their
> code to
> do the mapping as well (with a slightly different algorithm).
> 
> The basic approach to the mapping is to take each vertex normal
> (important, you must
> use textured gourard poly's so that the vertex normals are available)
> then rotate it
> using the local to world matrix. Then scale the rotated vector to be
> length ONE, and
> finally use:
> 
>         texture_u=(rotated_scaled_normal.x * (texture_width-1))/ONE;
>         texture_v=(rotated_scaled_normal.y * (texture_height-1))/ONE;
> 
> Repeat for each vertex normal and cache the results in a lookup table
> indexed
> via the vertex number.
> 
> Then go through the poly's section filling in the texture UV's of each
> primitive
> from the lookup table you generated (each vertex will have a UV pair,
> and the poly
> hold the index of the vertex). For a bit of extra pace (on models of <
> 512 vertices)
> put the UV cache in the scratch pad.
> 
> If you go back over old messages you'll find my code that does just
> this....
> 
> Craig.

Thanks for this! I did have your original source code that you posted
a while back, but until now I didn't fully understand it.

I believe the playstation 2 can do true environment mapping. I remember
seeing the gran turismo technical demo with proper reflections off the
cars. Or was I imagining things?

Anyway, many thanks.
Harvey.