how can I make texture from non power of 2 image

OpenGL OpenGL: Basic Coding
1

glu2DBuildMipmaps does that

glu2DBuildMipmaps is so slow

Is There another function which makes texture from non power of 2 image fastly?

2

slow??

well, write your own, it’s not very complicated

Jan

3

glu2DBuildMipmaps may not be the fastest way but since you only need to call it once its not a bottleneck at all.

4

or use an image manipulating program (such as GIMP) to rescale the texture images.

5

Hi,
You can use non-power-of-two textures with the txture_rectangle extension, it’s supported on both nVidia and Ati (with recent drivers, on old cards too).

6

If you want to go fast and the non power of 2 image is on the framebuffer, use glCopyTexSubImage to update the relevant part of the texture. If the non power of 2 image is on the CPU ram, use glTexSubImage to specify what is needed.

If you need mipmaps you can use :
glTexParameteri( GL_TEXTURE_2D, GL_GENERATE_MIPMAP_SGIS,
GL_TRUE );
See http://developer.nvidia.com/object/gdc2001_automatic_mipmap.html

Of course, when you map the power of 2 texture, try to mask the not updated parts by choosing carefully the texture coordinates.

7

Originally posted by Tzupy:
Hi,
You can use non-power-of-two textures with the txture_rectangle extension, it’s supported on both nVidia and Ati (with recent drivers, on old cards too).

I was a real fan of that method however, I have it in my image management API internally to all my apps.

This thing is broken. Really, it can’t be used for serious high-performance apps, it has way too much limitations unless you use a dedicated fp/vp to workaround that. The texture target change is the primary issue in my opinion.

Every time I add a feature I find myself saying “Oh %!#@, this feature will be much more complicated if I have to add support for rect textures”. I have support for it since it got out. It never showed of vital importance and it always gave problems.

Really, unless ARB_n_p_o_t or whatever it’s called gets supported, forget using NPOTD textures for generic purposes - simply resize them at runtime if you can.

I raccomand using the glu func (I never used it but it’s already there). If you’re not happy with that, implement your own.

Are you sure you really need them?

8

There is also gluScaleImage if you want to scale the image to be a power of 2 w/o building full mipmaps with gluBuild2DMipMaps. Of course, you’ll have to figure out what dimensions to scale to that are within a power of 2, but that would be a fairly simple task.

[This message has been edited by Deiussum (edited 01-07-2004).]