I'm learning OpenGL ES with the tutorial on raywenderlich.com http://www.raywenderlich.com/4404/opengl-es-2-0-for-iphone-tutorial-part-2-textures
When I get started to tweak the example project to grasp a UIView's content as the texture to get rendered, it's only black screen turns out just like:
The black view is the OpenGL ES view.
I used the code posted by Tommy in this post: Render contents of UIView as an OpenGL texture , and here is my version:
- (GLuint)createTexture:(UIView *)view
{
size_t width = CGRectGetWidth(view.layer.bounds) * [UIScreen mainScreen].scale;
size_t height = CGRectGetHeight(view.layer.bounds) * [UIScreen mainScreen].scale;
GLubyte * texturePixelBuffer = (GLubyte *) calloc(width * height * 4,
sizeof(GLubyte));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(texturePixelBuffer,
width, height, 8, width*4, colorSpace,
kCGImageAlphaPremultipliedLast |
kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
[view.layer renderInContext:context];
CGContextRelease(context);
GLuint texName;
glGenTextures(1, &texName);
glBindTexture(GL_TEXTURE_2D, texName);
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, texturePixelBuffer);
free(texturePixelBuffer);
return texName;
}
According to Open GL ES 2.0 Specification, texture can either be the power of two or not. But you must use
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_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);
to enable non-power-of-two texture support.
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