You still need to watch out for non-uniform flow control.įragment shaders also have access to the discard command. As such, they can use the majority of the texturing functions. Unlike every other shader stage, fragment shaders have implicit derivatives generated. Such depth-only rendering is used for shadow mapping operations as well as depth pre-pass optimizations. This is useful for doing rendering where the only useful output is the fragment's depth, and you want to use the depth computed by the system, rather than some other depth.
However, the depth and stencil values for the output fragment have the same values as the inputs. If no fragment shader is used, then the color values of the output Fragment have undefined values. The output of a fragment shader is a depth value, a possible stencil value (unmodified by the fragment shader), and zero or more color values to be potentially written to the buffers in the current framebuffers.įragment shaders take a single fragment as input and produce a single fragment as output.įragment shaders are technically an optional shader stage. Each fragment has a Window Space position, a few other values, and it contains all of the interpolated per-vertex output values from the last Vertex Processing stage. For each sample of the pixels covered by a primitive, a "fragment" is generated.
The fragment shader is the OpenGL pipeline stage after a primitive is rasterized. A Fragment Shader is the Shader stage that will process a Fragment generated by the Rasterization into a set of colors and a single depth value.
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