Rendering Texture Quad to Screen or FBO (OpenGL ES)
- by Usman.3D
I need to render the texture on the iOS device's screen or a render-to-texture frame buffer object. But it does not show any texture. It's all black.
(I am loading texture with image myself for testing purpose)
//Load texture data
UIImage *image=[UIImage imageNamed:@"textureImage.png"];
GLuint width = FRAME_WIDTH;
GLuint height = FRAME_HEIGHT;
//Create context
void *imageData = malloc(height * width * 4);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
//Prepare image
CGContextClearRect(context, CGRectMake(0, 0, width, height));
CGContextDrawImage(context, CGRectMake(0, 0, width, height), image.CGImage);
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
Simple Texture Quad drawing code mentioned here
//Bind Texture, Bind render-to-texture FBO and then draw the quad
const float quadPositions[] = { 1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
-1.0, -1.0, 0.0,
-1.0, -1.0, 0.0,
1.0, -1.0, 0.0,
1.0, 1.0, 0.0 };
const float quadTexcoords[] = { 1.0, 1.0,
0.0, 1.0,
0.0, 0.0,
0.0, 0.0,
1.0, 0.0,
1.0, 1.0 };
// stop using VBO
glBindBuffer(GL_ARRAY_BUFFER, 0);
// setup buffer offsets
glVertexAttribPointer(ATTRIB_VERTEX, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), quadPositions);
glVertexAttribPointer(ATTRIB_TEXCOORD0, 2, GL_FLOAT, GL_FALSE, 2*sizeof(float), quadTexcoords);
// ensure the proper arrays are enabled
glEnableVertexAttribArray(ATTRIB_VERTEX);
glEnableVertexAttribArray(ATTRIB_TEXCOORD0);
//Bind Texture and render-to-texture FBO.
glBindTexture(GL_TEXTURE_2D, GLid);
//Actually wanted to render it to render-to-texture FBO, but now testing directly on default FBO.
//glBindFramebuffer(GL_FRAMEBUFFER, textureFBO[pixelBuffernum]);
// draw
glDrawArrays(GL_TRIANGLES, 0, 2*3);
What am I doing wrong in this code?
P.S. I'm not familiar with shaders yet, so it is difficult for me to make use of them right now.
