shaders - What is a fragment in 3D graphics programming?

What is a fragment in a fragment shader? Wikipedia says that:

In general, a fragment can be thought of as the data needed to shade the pixel, plus the data needed to test whether the fragment survives to become a pixel (depth, alpha, stencil, scissor, window ID, etc.)

So is it textures, vertices or something else?

Answer

In computer graphics, a fragment is the data necessary to generate a single pixel's worth of a drawing primitive in the frame buffer.

This data may include, but is not limited to:

• raster position



• depth


• interpolated attributes (color, texture coordinates, etc.)


• stencil


• alpha


• window ID

As a scene is drawn, drawing primitives are rasterized into fragments which are textured and combined with the existing frame buffer. How a fragment is combined with the data already in the frame buffer depends on various settings. In a typical case, a fragment may be discarded if it is farther away than the pixel that is already at that location (according to the depth buffer). If it is nearer than the existing pixel, it may replace what is already there, or, if alpha blending is in use, the pixel's color may be replaced with a mixture of the fragment's color and the pixel's existing color, as in the case of drawing a translucent object.

In general, a fragment can be thought of as the data needed to shade the pixel, plus the data needed to test whether the fragment survives to become a pixel (depth, alpha, stencil, scissor, window ID, etc.)

From wikipedia