gl_FragCoord

Available only in the fragment language, is an input variable that contains the window relative coordinate (x, y, z, 1/w) values for the fragment. If multi-sampling, this value can be for any location within the pixel, or one of the fragment samples. This value is the result of fixed functionality that interpolates primitives after vertex processing to generate fragments. The z component is the depth value that would be used for the fragment's depth if no shader contained any writes to gl_FragDepth .

may be redeclared with the additional layout qualifier identifiers origin_upper_left or pixel_center_integer . By default, assumes a lower-left origin for window coordinates and assumes pixel centers are located at half-pixel centers. For example, the (x, y) location (0.5, 0.5) is returned for the lower-left-most pixel in a window. The origin of may be changed by redeclaring with the origin_upper_left identifier. The values returned can also be shifted by half a pixel in both x and y by pixel_center_integer so it appears the pixels are centered at whole number pixel offsets. This moves the (x, y) value returned by of (0.5, 0.5) by default to (0.0, 0.0) with pixel_center_integer .

If is redeclared in any fragment shader in a program, it must be redeclared in all fragment shaders in that program that have static use of . Redeclaring with any accepted qualifier affects only and . It has no affect on rasterization, transformation or any other part of the OpenGL pipeline or language features.

gl_FragDepth

Copyright 2011-2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. .