OpenGL 1.x easy question

[Baker]

Let's say I want to draw a single face of size 384 x 384 and I have texture wrap on.

I have a 128x128 texture and I want it to repeat 3 times both ways but only submit a single quad or triangle list, what texcoords do I use? I can't remember how to do this.

[If remember, I'll post own answer.... I've done this before ... I just can't remember ...]

[taniwha]

If wrap is on, then 0..3x0..3 will tile both ways 3 times (0..1 is the full width/height of the texture).

[Baker]

[Spike]

hrm?
an npot texture just refers to the number of pixels across, its texture coords still scale the same.
if you try uploading an npot texture with drivers that don't support npot, you get a gl error and an undefined image (thus white, if using glsl it appears black instead).
if the driver supports npot then 0-1 scales exactly the same as power-of-two textures do.
they'd be useless if they didn't.

the whole point of npot textures is that the hardware supports them exactly as it would a power-of-two texture. that's what makes it an actual gl feature instead of some upload hack that would be available in extensionless gl1.1.

[Baker]

[Spike]

you're trying to render a 2d image using npot? and trying to support power-of-two-only devices too, without scaling?
remember to move the edge coords inwards by 0.5*size or you'll see the padding as some sort of black border.
wrapping is only important if you've got a surface that tiles. you can always implement tiling using multiple surfaces.


many older cards that don't support npot do support rect textures. those may be a viable alternative for you?

[Baker]

[andrewj]

You can't make a padded texture tile properly -- it's either use the NPOT extension, or chop up your polygon into pieces which are the same size as the texture (which is pretty painful to code).

[leileilol]

[Spike]

by 'older' I include mobile chipsets too, though a fair number of those support regular npot textures in some limited form if only because they're so useful for 2d rendering.

but yeah, rect textures tend to have mipmaping limitations, as does limited npot support.