Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Fri, 7 Feb 1997 11:34:12 +0000
I suspect MIP mapping will be bringing in a higher level of MIP when
you have 1:1 texel:pixel correlation.
This won't solve the problem of sub pixel positioning, you'll get
aliasing without a bilinear filter but if you have a bilinear filter
with 1:1 correlation you'll have to have your pixels aligned with the
texels or you'll get a weighted value between texels.
When you get _really_ close you see the bilinear interpolation between
the nearest four samples. Use point sampling to avoid this but expect
aliasing problems at texel boundaries.
Cheers,
Angus.
On Feb 5, 5:05pm, Eric Heft wrote:
> Subject: Help with textures.
> Hello,
>
> Brief question:
>
> How do I get an inventor object with a texture, to display
> the texture *EXACTLY* the way its defined in the texture image?
> (at a range where the object is the same size as the texture)
>
> Background:
>
> I'm writting a program thats going to be used in vision research,
> and its important to be able to say exactly whats going on when we
> present a stimulus and before we can do the interesting objects we've
> got to get some pilot stuff out of the way.
>
> So, we need to present a checker board with nice sharp edges. I've
> created a rgb image file with the checker board. I figured I map this
> onto a simple object.
>
> *THE PROBLEM*
>
> If I bring the object close to me the edges of the checker board
> are blured! I've tried turning anti-aliasing on and off and it makes
> no difference. I've set the texture model to DECAL which at least
> gets rid of the shading problem :)
>
> In the man page for pfTexture there is a pfTexFilter function,
> could this be what I want? How would I use it with the model?
> Where can I look for more information? etc,etc :)
>
>
> Here is the basic inventor model I'm using.
>
> #Inventor V2.0 ascii
>
> Separator {
> Texture2 {
>
> model DECAL
> filename "chkbrd.rgb"
> }
> Material {
> ambientColor 1.0 1.0 1.0
> }
> Transform {
> translation 0 0 0
> scaleFactor 10.0 10.0 0.1
> }
> Cube {
> }
> }
>
>
>
> Thanks,
> Eric
>
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>-- End of excerpt from Eric Heft
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