Opengl: how to handle many textures/images?

Total opengl noob here.

I have a whole directory of images that I end up loading into memory and building textures from parts of these images. Constructing the textures from the subparts of these images on the fly is bogging the system down, but I won't know beforehand what portions of these images will need to be selected to build the textures. Is there a better way to handle this than creating a large number of textures? For instance, making one texture for each image and then sampling a subset of that texture to apply to each surface?

I can post code if it helps, but there is a lot of it. I was hoping for more of general guidelines开发者_C百科 and orientation towards using textures in an efficient way.

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Sounds to me like you just want to adjust your texture coordinates.

Texture coordinates are given between 0 and 1.

To draw the whole texture onto a quad, you could do something like this:

glTexCoord2f(0.0f, 0.0f);
glVertex3f(...)
glTexCoord2f(1.0f, 0.0f);
glVertex3f(...)
glTexCoord2f(1.0f, 1.0f);
glVertex3f(...)
glTexCoord2f(0.0f, 1.0f);
glVertex3f(...)

But to draw just one quarter of the texture onto the same quad: (Note the different values for glTexCoord)

glTexCoord2f(0.0f, 0.0f);
glVertex3f(...)
glTexCoord2f(0.5f, 0.0f);
glVertex3f(...)
glTexCoord2f(0.5f, 0.5f);
glVertex3f(...)
glTexCoord2f(0.0f, 0.5f);
glVertex3f(...)

Look up OpenGL texturing tutorial on the almighty Google.