Graphics Reference
In-Depth Information
Vertex Buffer/
Array Objects
Transform
Feedback
Array Objects
Feedback
Primitive
Assembly
Vertex Shader
r
Rasterization
API
Textures
Fragment
Fragment
Shader
Per-Fragment
Operations
Framebuffer
Figure 10-1
OpenGL ES 3.0 Programmable Pipeline
Readers who are new to the programmable fragment pipeline but have
worked with OpenGL ES 1.x (or earlier versions of desktop OpenGL) are
probably familiar with the fixed-function fragment pipeline. Before diving
into details of the fragment shader, we think it is worthwhile to briefly
review the old fixed-function fragment pipeline. This will give you an
understanding of how the old fixed-function pipeline maps into fragment
shaders. It's a good way to start before moving into more advanced
fragment programming techniques.
In OpenGL ES 1.1 (and fixed-function desktop OpenGL), you had a
limited set of equations that could be used to determine how to combine
the various inputs to the fragment shader. In the fixed-function pipeline,
you essentially had three inputs you could use: the interpolated vertex
color, the texture color, and the constant color. The vertex color would
typically hold either a precomputed color or the result of the vertex
lighting computation. The texture color came from fetching from
whichever texture was bound using the primitive's texture coordinates
and the constant color could be set for each texture unit.
