Question

As I know, OpenGL has highly supported NPOT textures since 3.0. Now I’ m facing an bizarre phenomenon that NPOT texture cannot be allocated with precise corresponding data. Words are plain. My testing code is as below.

glGenTextures(1, &texVoxels);
glBindTexture(GL_TEXTURE_3D, texVoxels);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

int width = 513;
int height = 513;
int depth = 513;
unsigned char *data = new unsigned char[width*height*depth];
memset(data, 0, sizeof(unsigned char)*width*height*depth);

glTexImage3D(GL_TEXTURE_3D, 0, GL_LUMINANCE8, width, height,depth, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, data);

delete []data;
data = NULL;

As code shown above, I need to allocate an NPOT cubic texture of 2^N +1. But program will exit error on glTexImage3D(). The error, I think, is caused by “the size of data less than the texture needed”. Because if I allocate data larger enough, the program will pass.

How could I use NPOT texture and allocate data like this? Even though when the size of data is larger enough the program passes, I am really not sure about how data exactly corresponds to the texture location then.

PS. My graphic card is quadro fx 4800, which supports OpenGL 3.3.

Answer 1

You probably need to set pixel storage parameters. Most importantly the row alignment. Try adding a

glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

before calling glTexImage3D.