Im trying to render a non power of 2 texture using a model class

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Asked: May 23, 20262026-05-23T21:19:53+00:00 2026-05-23T21:19:53+00:00

Im trying to render a non power of 2 texture using a model class

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Im trying to render a non power of 2 texture using a model class that creates a texture and stores it’s ID and size (thanks to ADC and another stackoverflow member), and additional code the create VBO’s and render it (The code for VBO’s and rendering is for testing purposes, it is properly divided in my models).

When I use this code, but remove the texture-specific code, it works fine. When adding the texture specific code however, it only renders what I believe to be the bottom-right pixel, from trying out multiple complex images and using DigitalColor Meter to check the images and output.

I don’t suppose that texture coordinates have to be specified explicitly when using this setup, and if they do, how would I?

Main OpenGL Code

    // Create vertex buffer
    GLuint memoryPointer = 0;
    GLuint colourMemoryPointer = 0;

    GLfloat *vertices;
    size_t vertex_size = 0;

    int check = AllocateVertexBuffer(2, 4, &vertices, &vertex_size);
    CDMeshVertexesCreateRectangle(200, 200, vertices);


    // Create colour buffer
    GLfloat *colors;
    size_t color_size;

    int check2 = AllocateVertexBuffer(4, 4, &colors, &color_size);
    CDMeshColorsCreateGrey(1.0, 4, colors);


    // Create texture buffer
    CDTexture *texture = [CDTexture loadPngTexture:@"Rawr"];

    // Allocate the buffer
    glGenBuffers(1, &memoryPointer);
    // Bind the buffer object (tell OpenGL what to use)
    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);

    // Allocate space for the VBO
    glBufferData(GL_ARRAY_BUFFER, vertex_size, vertices, GL_STATIC_DRAW);


    // Allocate the buffer
    glGenBuffers(1, &colourMemoryPointer);
    // Bind the buffer object (tell OpenGL what to use)
    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);

    // Allocate space for the VBO
    glBufferData(GL_ARRAY_BUFFER, color_size, colors, GL_STATIC_DRAW);

    glEnableClientState(GL_VERTEX_ARRAY); // Activate vertex coordinates array
    glEnableClientState(GL_COLOR_ARRAY);

    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);
    glVertexPointer(2, GL_FLOAT, 0, 0);   

    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
    glColorPointer(4, GL_FLOAT, 0, 0);

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture.ID);
    glTexCoordPointer(2, GL_FLOAT, 0, 0);

    //[texture render];

    //render
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    glDisableClientState(GL_VERTEX_ARRAY); // Deactivate vertex coordinates array
    glDisableClientState(GL_COLOR_ARRAY);

    free(vertices);
    free(colors);

CDTexture loadPngTexture: Method

CFURLRef textureURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(),
                                              (CFStringRef)fileName,
                                              CFSTR("png"),
                                              NULL);

NSAssert(textureURL, @"Texture name invalid");

// Get the image source using a file path
CGImageSourceRef myImageSourceRef = CGImageSourceCreateWithURL(textureURL, NULL);
NSAssert(myImageSourceRef, @"Invalid Image Path.");
NSAssert((CGImageSourceGetCount(myImageSourceRef) > 0), @"No Image in Image Source.");

// Get the image reference using the source reference, -_-
CGImageRef myImageRef = CGImageSourceCreateImageAtIndex (myImageSourceRef, 0, NULL);
NSAssert(myImageSourceRef, @"Image not created.");

// Start gathering data from the image, before releasing it
GLuint myTextureName;
size_t width = CGImageGetWidth(myImageRef);
size_t height = CGImageGetHeight(myImageRef);
CGRect rect = {{0, 0}, {width, height}};
void * myData = calloc(width * 4, height);
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGContextRef myBitmapContext = CGBitmapContextCreate (myData,
                                                      width, height, 8,
                                                      width*4, space,
                                                      kCGBitmapByteOrder32Host |
                                                      kCGImageAlphaPremultipliedFirst);

CGColorSpaceRelease(space);
// Flip so that it isn't upside-down
CGContextTranslateCTM(myBitmapContext, 0, height);
CGContextScaleCTM(myBitmapContext, 1.0f, -1.0f);
CGContextSetBlendMode(myBitmapContext, kCGBlendModeCopy);
CGContextDrawImage(myBitmapContext, rect, myImageRef);
CGContextRelease(myBitmapContext);

glEnable(GL_TEXTURE_RECTANGLE_ARB);

// Generate texture buffer
glGenTextures(1, &myTextureName);

// Bind buffer for use
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, myTextureName);

// Set storage methods
glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

// Set the parameter required for non power of two textures
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
                GL_TEXTURE_MIN_FILTER, GL_LINEAR);

// Load the texture data into the buffer
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGBA8, width, height,
             0, GL_BGRA_EXT, GL_UNSIGNED_INT_8_8_8_8_REV, myData);

// Free the data used, as it's now in the buffer
free(myData);

// Return information on texture object
CDTexture *texture = [[CDTexture alloc] init];

texture.ID = myTextureName;
texture.size = NSMakeSize(width, height);

return texture;

UPDATE
I’ve tried using a texture pointer to define the area, and this results in the same problem. The colour/texture it draws will do so even without binding and using a pointer. I have also tried enabling and disabling GL_TEXTURE_COORD_ARRAY before and after it is used and rendered, and results in the same problem.

Unless i’ve done something wrong, the problem doesn’t seem related with texture pointers.

GLfloat texCoords[8] = {
0.0, 0.0,
0.0, 1.0,
1.0, 1.0,
1.0, 0.0
};

...

glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
glColorPointer(4, GL_FLOAT, 0, 0);

glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture.ID);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);

//[texture render];

//render
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

UPDATE 2
I’ve tried obtaining an error code from OpenGL to try and solve the problem, but no error codes have been printed.

UPDATE 3
I have tried using a different method to get raw image data, and the same result happens (albeit with some discolouration, as I must not be using the right colour settings). OpenGL’s interpretation of the data must be flawed here. I have experimented with glPixelStorei() but nothing has changed so far. As OpenGL isn’t reporting any error, it must be with the programs interpretation of the data, so either the parameters I have set for how data is stored, or vertex problems that is causing only 1 pixel to be displayed, although because of this precision, it is most likely to be parameters.

New process for raw image data (thanks to another stackoverflow user). Posted for reference.

 NSBitmapImageRep *theImage;
int bitsPPixel, bytesPRow;
NSSize size;
unsigned char *theImageData;

NSData* imgData = [NSData dataWithContentsOfFile:fileName options:NSUncachedRead error:nil];  // use FileURL

theImage = [NSBitmapImageRep imageRepWithData:imgData]; 


if( theImage != nil )
{
    bitsPPixel = [theImage bitsPerPixel];
    bytesPRow = [theImage bytesPerRow];
    size.width = [theImage pixelsWide];
    size.height = [theImage pixelsHigh];
}

enter code here

UPDATE 4
Changed to GL_TEXTURE_2D for efficiency. The bottom-left pixel is still only being rendered. Here is the full order of the code:

// Create vertex buffer
    GLuint memoryPointer = 0;
    GLuint colourMemoryPointer = 0;

    GLfloat *vertices;
    size_t vertex_size = 0;

    AllocateVertexBuffer(2, 4, &vertices, &vertex_size);
    CDMeshVertexesCreateRectangle(200, 200, vertices);


    // Create colour buffer
    GLfloat *colors;
    size_t color_size;

    AllocateVertexBuffer(4, 4, &colors, &color_size);
    CDMeshColorsCreateGrey(1.0, 4, colors);

    // Create Texture UV Coordinates
    GLfloat *texture;
    size_t texture_size;
    AllocateVertexBuffer(4, 2, &texture, &texture_size);
    CDMeshVertexesCreateRectangle(1, 1, texture);

    // Create texture buffer
    NSString *fileName = @"Rawr3";

    CFURLRef textureURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(),
                                                  (CFStringRef)fileName,
                                                  CFSTR("png"),
                                                  NULL);

    NSAssert(textureURL, @"Texture name invalid");

    // Get the image source using a file path
    CGImageSourceRef myImageSourceRef = CGImageSourceCreateWithURL(textureURL, NULL);
    NSAssert(myImageSourceRef, @"Invalid Image Path.");
    NSAssert((CGImageSourceGetCount(myImageSourceRef) > 0), @"No Image in Image Source.");

    // Get the image reference using the source reference, -_-
    CGImageRef myImageRef = CGImageSourceCreateImageAtIndex (myImageSourceRef, 0, NULL);
    NSAssert(myImageSourceRef, @"Image not created.");

    // Start gathering data from the image, before releasing it
    GLuint myTextureName;
    size_t width = CGImageGetWidth(myImageRef);
    size_t height = CGImageGetHeight(myImageRef);
    CGRect rect = {{0, 0}, {width, height}};    //Doesnt need fiddling
    void * myData = calloc(width * 4, height); //Fiddled
    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
    CGContextRef myBitmapContext = CGBitmapContextCreate (myData,
                                                          width, height, 8,
                                                          width*4, space,
                                                          kCGBitmapByteOrder32Host |
                                                          kCGImageAlphaPremultipliedFirst);

    CGColorSpaceRelease(space);
    // Flip so that it isn't upside-down
    CGContextTranslateCTM(myBitmapContext, 0, height);
    CGContextScaleCTM(myBitmapContext, 1.0f, -1.0f);
    CGContextSetBlendMode(myBitmapContext, kCGBlendModeCopy);
    CGContextDrawImage(myBitmapContext, rect, myImageRef);
    CGContextRelease(myBitmapContext);

    // Generate texture buffer
    glGenTextures(1, &myTextureName);

    // Bind buffer for use
    glBindTexture(GL_TEXTURE_2D, myTextureName);

    // Set storage methods
    glTexParameteri(GL_TEXTURE_2D,
                    GL_TEXTURE_STORAGE_HINT_APPLE,
                    GL_STORAGE_CACHED_APPLE);

    glPixelStorei(GL_UNPACK_CLIENT_STORAGE_APPLE, GL_TRUE);

    // Set clamping and rendering preferences
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, 
                    GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
                    GL_NEAREST);

    // Load the texture data into the buffer
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height,
                 0, GL_BGRA_EXT, GL_UNSIGNED_INT_8_8_8_8_REV, myData);

    glGetError();

    // Free the data used, as it's now in the buffer
    free(myData);

    // Return information on texture object
    CDTexture *textureObj = [[CDTexture alloc] init];

    textureObj.ID = myTextureName;
    textureObj.size = NSMakeSize(width, height);

    // Allocate the buffer
    glGenBuffers(1, &memoryPointer);
    // Bind the buffer object (tell OpenGL what to use)
    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);

    // Allocate space for the VBO
    glBufferData(GL_ARRAY_BUFFER, vertex_size, vertices, GL_STATIC_DRAW);


    // Allocate the buffer
    glGenBuffers(1, &colourMemoryPointer);
    // Bind the buffer object (tell OpenGL what to use)
    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);

    // Allocate space for the VBO
    glBufferData(GL_ARRAY_BUFFER, color_size, colors, GL_STATIC_DRAW);

    glEnableClientState(GL_VERTEX_ARRAY); // Activate vertex coordinates array
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnable(GL_TEXTURE_2D);

    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);
    glVertexPointer(2, GL_FLOAT, 0, 0);   

    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
    glColorPointer(4, GL_FLOAT, 0, 0);

    glBindTexture(GL_TEXTURE_2D, textureObj.ID);
    glTexCoordPointer(2, GL_FLOAT, 0, texture);

    GetGLError();

    //render
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    glDisableClientState(GL_VERTEX_ARRAY); // Deactivate vertex coordinates array
    glDisableClientState(GL_COLOR_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisable(GL_TEXTURE_2D);

    glDeleteBuffers(1, &memoryPointer);
    glDeleteBuffers(1, &colourMemoryPointer);
    GLuint texID = textureObj.ID;
    glDeleteBuffers(1, &texID);

    free(vertices);
    free(colors);
    free(texture);


}

UPDATE 5
From glTexImage2D(), it will render the bottom-left pixel of the texture even if I don’t bind the texture and add coordinates for it, which seems strange, considering that it should be drawn using glTexCoordPointer().

UPDATE 6
Probably the last update, used the texture initialisation code with another more, ‘manual’ technique of drawing and it worked fine. I have removed the Apple specific elements. When removing the colour VBO and pointer from this code, a white box is still rendered for some odd reason. The problem is with the VBO’s, but I cant see why. GL_TEXTURE_RECTANGLE_ARB is just being used for my coloured texture right now, will be changed when this problem is solved.

// Create vertex buffer
    GLuint memoryPointer = 0;
    GLuint colourMemoryPointer = 0;

    GLfloat *vertices;
    size_t vertex_size = 0;

    AllocateVertexBuffer(2, 4, &vertices, &vertex_size);
    CDMeshVertexesCreateRectangle(200, 200, vertices);

    GetGLError();

    // Create colour buffer
    GLfloat *colors;
    size_t color_size;

    AllocateVertexBuffer(4, 4, &colors, &color_size);
    CDMeshColorsCreateGrey(0.4, 4, colors);

    // Allocate the buffer
    glGenBuffers(1, &memoryPointer);
    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);
    glBufferData(GL_ARRAY_BUFFER, vertex_size, vertices, GL_STATIC_DRAW);

    // Allocate the buffer
    glGenBuffers(1, &colourMemoryPointer);
    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
    glBufferData(GL_ARRAY_BUFFER, color_size, colors, GL_STATIC_DRAW);

    // Enable client states for drawing the various arrays
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    // Bind each buffer and use the VBO's to draw (apart from the texture buffer)
    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);
    glVertexPointer(2, GL_FLOAT, 0, 0);   

    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
    glColorPointer(4, GL_FLOAT, 0, 0);

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, myTextureName); //
    glTexCoordPointer(2, GL_FLOAT, 0, texture);

    //render
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    // Disale client states as were done with them.
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisable(GL_TEXTURE_RECTANGLE_ARB);

    GetGLError();

    // Delete buffers to avoid problems
    glDeleteBuffers(1, &memoryPointer);
    glDeleteBuffers(1, &colourMemoryPointer);
    glDeleteBuffers(1, &myTextureName);

    free(vertices);
    free(colors);
    free(texture);

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1 Answer

Editorial Team · Answer 1 · 2026-05-23T21:19:54+00:00

I solved the problem (finally) by creating a Vertex Buffer Object (VBO) for the texture, instead of trying to supply vertex data directly to glTextureCoordPointer(). I guess the lesson here is that if you are going to use VBO’s, use them for everything! For reference, here is the complete code:

Texture Creation

// Create texture buffer, start with the name of the image.
    NSString *fileName = @"Rawr";

    CFURLRef textureURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(),
                                                  (CFStringRef)fileName,
                                                  CFSTR("png"),
                                                  NULL);

    NSAssert(textureURL, @"Texture name invalid");

    // Get the image source using a file path
    CGImageSourceRef myImageSourceRef = CGImageSourceCreateWithURL(textureURL, NULL);
    NSAssert(myImageSourceRef, @"Invalid Image Path.");
    NSAssert((CGImageSourceGetCount(myImageSourceRef) > 0), @"No Image in Image Source.");

    // Get the image reference using the source reference, -_-
    CGImageRef myImageRef = CGImageSourceCreateImageAtIndex (myImageSourceRef, 0, NULL);
    NSAssert(myImageSourceRef, @"Image not created.");

    // Start gathering data from the image, before releasing it
    GLuint myTextureName;
    size_t width = CGImageGetWidth(myImageRef);
    size_t height = CGImageGetHeight(myImageRef);
    CGRect rect = {{0, 0}, {width, height}};    //Doesnt need fiddling
    void * myData = calloc(width * 4, height); //Fiddled
    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
    CGContextRef myBitmapContext = CGBitmapContextCreate (myData,
                                                          width, height, 8,
                                                          width*4, space,
                                                          kCGBitmapByteOrder32Host |
                                                          kCGImageAlphaPremultipliedFirst);

    CGColorSpaceRelease(space);
    // Flip so that it isn't upside-down
    CGContextTranslateCTM(myBitmapContext, 0, height);
    CGContextScaleCTM(myBitmapContext, 1.0f, -1.0f);
    CGContextSetBlendMode(myBitmapContext, kCGBlendModeCopy);
    CGContextDrawImage(myBitmapContext, rect, myImageRef);
    CGContextRelease(myBitmapContext);

    GetGLError();

    // The extension GL_TEXTURE_RECTANGLE_ARB can be used for non-power of two textures, but it is slower than GL_TEXTURE_2D and not
    // supported by all graphics cards.
    glEnable(GL_TEXTURE_RECTANGLE_ARB);
    glGenTextures(1, &myTextureName);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, myTextureName);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER,GL_NEAREST);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER,GL_NEAREST);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, myData);
    //glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT ,GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_RECTANGLE_ARB,myTextureName, 0);
    free(myData);

VBO Creation

// Create vertex buffer
    GLuint memoryPointer = 0;
    GLuint colourMemoryPointer = 0;
    GLuint texPointer = 0;

    GLfloat *vertices;
    size_t vertex_size = 0;

    AllocateVertexBuffer(2, 4, &vertices, &vertex_size);
    CDMeshVertexesCreateRectangle(200, 200, vertices);

    GetGLError();

    // Create colour buffer
    GLfloat *colors;
    size_t color_size;

    AllocateVertexBuffer(4, 4, &colors, &color_size);
    CDMeshColorsCreateGrey(0.0, 4, colors);

    // Create Texture UV Coordinates
    GLfloat *texture;
    size_t texture_size;
    AllocateVertexBuffer(2, 4, &texture, &texture_size);
    CDMeshVertexesCreateRectangle(200, 200, texture);

    // Allocate the vertex VBO
    glGenBuffers(1, &memoryPointer);
    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);
    glBufferData(GL_ARRAY_BUFFER, vertex_size, vertices, GL_STATIC_DRAW);

    // Allocate the colour VBO
    glGenBuffers(1, &colourMemoryPointer);
    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
    glBufferData(GL_ARRAY_BUFFER, color_size, colors, GL_STATIC_DRAW);

    // Allocate the texture VBO
    glGenBuffers(1, &texPointer);
    glBindBuffer(GL_ARRAY_BUFFER, texPointer);
    glBufferData(GL_ARRAY_BUFFER, texture_size, texture, GL_STATIC_DRAW);

Rendering and Deleting VBO and Data

// Enable client states for drawing the various arrays
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    // Bind each buffer and use the VBO's to draw
    glBindBuffer(GL_ARRAY_BUFFER, memoryPointer);
    glVertexPointer(2, GL_FLOAT, 0, 0);   

    glBindBuffer(GL_ARRAY_BUFFER, colourMemoryPointer);
    glColorPointer(4, GL_FLOAT, 0, 0);

    glBindBuffer(GL_ARRAY_BUFFER, texPointer);
    glTexCoordPointer(2, GL_FLOAT, 0, 0);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, myTextureName);

    // RENDER!
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    // Disale client states as were done with them.
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisable(GL_TEXTURE_RECTANGLE_ARB);

    GetGLError();

    // Delete buffers when they arent being used.
    glDeleteBuffers(1, &memoryPointer);
    glDeleteBuffers(1, &colourMemoryPointer);
    glDeleteBuffers(1, &myTextureName);
    glGenTextures(GL_TEXTURE_RECTANGLE_ARB, 0);

    // Free vertexes when done using them
    free(vertices);
    free(colors);
    free(texture);

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Im trying to render a non power of 2 texture using a model class

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