Fragment shader

A fragment shader is a programmable stage of the rasterization pipeline that computes values for a fragment, such as its output color and optionally its depth. It receives interpolated data from rasterized primitives and can use texture mapping to sample an image. A fragment is a candidate contribution; later tests and blending determine what reaches the final digital image.^[ref]

For example, a shader can multiply a surface's interpolated color by a sampled image to decorate a triangle. A fragment hidden behind a nearer opaque surface may fail the depth buffer test. With multiple samples per pixel, fragments, shader invocations and final pixels need not correspond one to one.