Hello everyone,

I have a few questions about OpenGL that I could not find (direct) answers to with Google regarding memory allocation.

First, from what I've read, the function glTexImage2D() seems to be the function that allocates VRAM for textures. Is this correct?

Second, do I need to free this memory manually, or does OpenGL automatically do this? If I need to free it manually, which function(s) do I use?

Third, will glTexImage2D() allow me to alter a texture image that already exists in VRAM (providing I bind the appropriate texture and use the same dimensions)? Or do I need to first delete the texture and create a new one before attempting this?

For example...

void Init(void) {

//init stuff

glGenTextures(1, &my_texture);

}

void DrawSomething(void) {

glBindTexture(my_texture);

glTexImage2D(GL_TEXTURE_2D, 0, my_data_pix_format, my_width, my_height, 0, my_data_byte_format, my_pixels);

glBegin(GL_QUADS);

//render something

glEnd(GL_QUADS);

}

void Shutdown(void) {

//destory stuff

glDeleteTextures(1, &my_texture);

}

If DrawSomething() were to be called multiple times (i.e. every frame), and if the only thing that were to change would be my_pixels, would there be a memory leak?

Thank you.

Yes.

No you do not need to free the memory.

Why you would want to do this? Creating a texture every frame is really slow, its far better to create textures in the load up phase and just bind the correct one, or ones to create an effect.
[edit]if you really wanted to do this there are better ways[/edit]

I need to dynamically draw strings using OpenGL. The problem is that the string contents are arbitrary--I can't pre-render them

Fortunately, I only need to regenerate the texture every 50-ish frames. You see, I'm developing a game, and was confronted with the need to render HUD elements that included potentially arbitrary strings.

Thank you for your responses!

PS Could you direct me to the "better ways" you mentioned? Thanks

For the drawing of text you may want to look at nehe's lesson 13 (one of the linux ports at the bottom). Basically You load in a font and place the letters into a display list(which are quick) and draw from there.