what's a texture indirection?

i’m new in vertex/fragment programming and i’ve heard some concepts that i don’t understand but i wish to, so could anyone, please, explain-me what texture indirections and dependent-reads are?

that’s how i understand this:


  1. read texture A
  2. use values from A to lookup into texture B

texture indirections:

  1. read the vertex mapping into register A
  2. access texture using register A instead of using the vertex mapping directly.

btw. this only applies to fp’s.(vp’s don’t support texture accesses)