Question

I’m currently developing an iOS application (iPad and iPhone) that uses OpenGL ES 1.0 to render some basic textures. I use atlases to store and present my textures.

My main atlas is relatively large (2000×2000) but my internal algorithms load and resize the texture to 2048×2048 since OpenGL ES only accepts power of 2 sized textures. I’m able to draw the tiles, everything’s fine on this side.

I’m facing a serious memory leak every time I try to load and unload (destroy) the texture. This should happen in the final version but I needed to make sure that my loading and unloading were fine. In memory the texture occupies 2048x2048x4 (RGBA) bytes = 16MB approx.
This is a huge amount of bytes so you understand that the problem is pretty annoying to me (iOS kills the application after a few minutes..)

When I load a texture, Instruments indicates that the overall memory used by the application increases by 16MB this is correct (I use the “Real Memory” column). The problem occurs when I need to destroy the texture to free all the possible bytes used by it: it never looses the 16MB…and since I load and unload in a loop, the memory keeps being used and never freed.

Here’s how I load the textures:

GLubyte *outData = malloc((_dataWidth * _dataHeight * 4) * sizeof(*outData));
GLuint _texture; // declared as un instance variable so its address never changes
glGenTextures(1, &_texture);
glBindTexture(GL_TEXTURE_2D, _texture);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, _dataWidth, _dataHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, outData);
free(outData);

Here’s how I unload the texture (this is called, I checked)

glDeleteTextures(1, &_texture);

I used glGetError() everywhere to check if an error occurs but it always returns 0 (even after the glDeleteTexture).

Does anybody have an idea?
Thank you!

Answer 1

Make sure that you destroy your texture on the same thread, where you’ve created your context. If you’re doing any GL calls without context there would be no errors.