Trying to render a texture using a framebuffer always results in a white texture

Question

Using a couple of posts here in StackOverflow, I created what should be a simple rendering to a texture using a framebuffer.

The problem here is that it does not work. Something is broken in the mix since my last texture is just a white square. I am not getting any gl errors. Here is my code.

Declare instance variables.

GLuint texture;
GLuint textureFrameBuffer;

Generate texture and framebuffer.

    glGetError();

    //Generate the texture that we will draw to (saves us a lot of processor).
    glEnable(GL_TEXTURE_2D);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

    // Use OpenGL ES to generate a name for the texture.
    // Pass by reference so that our texture variable gets set.
    glGenTextures(1, &texture);

    // Bind the texture name. 
    glBindTexture(GL_TEXTURE_2D, texture);

    // Specify a 2D texture image, providing a pointer to the image data in memory.
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 512, 128, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);

    //Create a frame buffer to draw to. This will allow us to directly edit the texture.
    GLint oldFBO;
    glGetIntegerv(GL_FRAMEBUFFER_BINDING_OES, &oldFBO);
    glGenFramebuffersOES(1, &textureFrameBuffer);
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, textureFrameBuffer);
    glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, texture, 0);

    glBindFramebufferOES(GL_FRAMEBUFFER_OES, oldFBO);

    GLenum err = glGetError();
    if (err != GL_NO_ERROR)
    {
        NSLog(@"Error on framebuffer init. glError: 0x%04X", err);
    }

Draw a large line in the framebuffer.

glGetError();

GLint oldFBO;
glGetIntegerv(GL_FRAMEBUFFER_BINDING_OES, &oldFBO);

//Bind our frame buffer.
glBindFramebufferOES(GL_FRAMEBUFFER_OES, textureFrameBuffer);

//Clear out the texture.
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

//Draw the letters to the frame buffer. (calls glDrawArrays a bunch of times, binds various textures, etc.) Does everything in 2D.
[self renderDialog:displayString withSprite:displaySprite withName:displaySpriteName];

//Unbind the frame buffer.
glBindFramebufferOES(GL_FRAMEBUFFER_OES, oldFBO);

GLenum err = glGetError();
if (err != GL_NO_ERROR)
{
    NSLog(@"Error on string creation. glError: 0x%04X", err);
}

Draw it.

    glColor4f(1.0f, 1.0f, 1.0f, 1.0f);

    glGetError();

    //Draw the text.
    [EAGLView enable2D];

    //Push the matrix so we can keep it as it was previously.
    glPushMatrix();

    //Store the coordinates/dimensions from the rectangle.
    float x = 0;
    float y = [Globals getPlayableHeight] - dialogRect.size.height;
    float w = [Globals getPlayableWidth];
    float h = dialogRect.size.height;

    // Set up an array of values to use as the sprite vertices.
    GLfloat vertices[] =
    {
        x,      y,
        x,      y+h,
        x+w,    y+h,
        x+w,    y
    };

    // Set up an array of values for the texture coordinates.
    GLfloat texcoords[] =
    {
        0,          0,
        0,          h / 128,
        w / 512,    h / 128,
        w / 512,    0
    };

    //Render the vertices by pointing to the arrays.
    glVertexPointer(2, GL_FLOAT, 0, vertices);
    glTexCoordPointer(2, GL_FLOAT, 0, texcoords);

    // Set the texture parameters to use a linear filter when minifying.
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    //Allow transparency and blending.
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    //Enable 2D textures.
    glEnable(GL_TEXTURE_2D);

    //Bind this texture.
    [EAGLView bindTexture:texture];

    //Finally draw the arrays.
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    //Restore the model view matrix to prevent contamination.
    glPopMatrix();

    GLenum err = glGetError();
    if (err != GL_NO_ERROR)
    {
        NSLog(@"Error on draw. glError: 0x%04X", err);
    }

Any external things that I mentioned work fine in other contexts. Any ideas? I know almost nothing about framebuffers, so any troubleshooting help would be great.

Answer 1

. GL_TEXTURE_MIN_FILTER , , . , , , , , .

, GL , . , , glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) , GL_FRAMEBUFFER_COMPLETE_OES.