cg

I cannot seem to understand this, shouldn't the derivative/change along the U or V coordinate in a 2d texture/array be single dimension variable as we are checking it only along ddx (U coordinate) or ddy (V coordinate)? There are 4 distinct partial derivatives here: du/dx, dv/dx, du/dy, and dv/dy. None of those four values need be zero, unless the texture image coordinates happen to be perfectly aligned to the display screen axes. In general the texture coordinate axes need not be aligned to the screen display axes. X and Y (display viewport axes) are not the same directions as U and V

This question already has an answer here: What are Vertex and Pixel shaders? 5 answers I've read some tutorials regarding Cg, yet one thing is not quite clear to me. What exactly is the difference between vertex and fragment shaders? And for what situations is one better suited than the other? The Surrican A fragment shader is the same as pixel shader. One main difference is that a vertex shader can manipulate the attributes of vertices. which are the corner points of your polygons. The fragment shader on the other hand takes care of how the pixels between the vertices look. They are

I am using the following code to perform some manipulations on the image that I loaded, but I find that the display becomes blurry when it is on the retina display - (UIImage*)createImageSection:(UIImage*)image section:(CGRect)section { float originalWidth = image.size.width ; float originalHeight = image.size.height ; int w = originalWidth * section.size.width; int h = originalHeight * section.size.height; CGContextRef ctx = CGBitmapContextCreate(nil, w, h, 8, w * 8,CGImageGetColorSpace([image CGImage]), kCGImageAlphaPremultipliedLast); CGContextClearRect(ctx, CGRectMake(0, 0, originalWidth *