Re: NEED HELP ON TEXTURE MAPPING!
Mike Desrochers (desrochers++at++poster.cae.ca)
Fri, 3 Jul 1998 09:10:41 -0400
>
> My satellite textures are 2048x2048 each and between these pieces you
> can observe an annoying miscolored line when they are mapped. I
> figure this is due to Performer's method of interpolating, or
> blurring, the texture pixels to texels so they cover the whole surface.
> I have come the the conclusion (right or wrong?) that Performer
> filters the texture with some kind of average kernel, and that in
> the outer borders of the texture the pixels are blurred with the pixels
> on the opposite side of the image. This way unwanted lines with
> different colors appear between the texture pieces and in the
> outer borders of the terrain.
>
I would also check that the texture mapping coordinates are correct at the
boundaries of the textures to make sure the assumption above is your only
problem. It does not take much error in the texture U,V values for the eye to
pick up a mapping discontinuity between the textures.
>
> Is there anyone who knows how this phenomenon can be avoided?
> I guess one either would want to totally eliminate the average
> filtering between the different texture pieces, or perhaps it would
> be even better if one could just avoid filtering the pixels with the
> ones on the opposite side.
>
You should do your own filtering off line, and filter the texture with the 8
ajoining textures to get a perfect match! After filtering you then load each
LOD image of the texture as required. We have done this in the past, although
not with a large database, so I am not sure of the additional complexities
introduced by wanting to load your own MipMap LODs into the texture hardware.
I think this is the only sure way to get rid of the image discontinuities for
a global texturing scheme as you described.
Mike Desrochers
Senior Engineering Specialist
desrochers++at++cae.ca
m.desrochers++at++computer.org
mailto:desrochers++at++cae.ca
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on Mon Aug 10 1998 - 17:57:40 PDT