Path: chuka.playstation.co.uk!news
From: Jim <jim@micronetics.com>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Texture Wrapping
Date: Wed, 06 Aug 1997 11:46:39 +0100
Organization: PlayStation Net Yaroze (SCEE)
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References: <33E7381E.E55C5787@micronetics.com> <33E84C2C.6C25@interactive.sony.com>
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Developer Support wrote:
> 
> Jim wrote:
> >
> > Could be a silly question.
> >
> > Is there a way to get a texture to repeat itself over a large poly?
> > Presently I have multiple polys each with a single texture, but I could
> > vastly reduce the vertex and normal calcs if I had just one large poly
> > but with a repeating tex map.
> 
> If you have a 256x256 texture then it automatically wraps (but it
> doesn't look right when the poly crosses the edges). What you could do
> is load a smaller texture repeatedly in vram until it fills 256x256,
> this will only work if the polygon fits into 256x256 texel area.
> 
> If you can tell me more about polygon and texture sizes I maybe able to
> come up with some better ideas.
> 
> Stuart

Stuart, 

Thanks for the reply.

Here is my reasoning.  I have a polygon (lots infact) that are 400x400
with a texture (64x64), was (128x128) but that affected performance too
much.  The texutures are 16bit direct colour.
Could I set up the gpu to say draw one 400x800 polygon (for example) but
wrap the texture at 400x400 so the result would be the same as drawing
two planar connected 400x400 polys?

As an aside is there any noticable speed difference between 16 direct, 4
and 8 bit textures?  I would assume 4 and 8 bit a tad slower because of
the clut lookup before it translates into a 16 direct in the frame
buffer as it draws the textured poly.

Another aside, how does texture caching work?  It is best to group polys
with the same textures together to avoid texture cache misses?  Is it
true I can only cache 32x32 16bit direct textures?  So would I see more
of a speed increase if I make the textures 32x32, than when I went from
128x128 to 64x64, because it will now fit in the cache?


Cheers

-JiM