OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Combining Special Functions

In addition to all of the special texturing functions, several more variants of these functions exist that combine features from multiple variants. For example, if you want to do projective texturing with an explicit level-of-detail or gradients (each is described in “Explicit Gradient Specification” on Page 340), then you can use the combined functions textureProjLod or textureProjGrad, respectively. The combined functions using a 2D sampler are shown below. Variants of almost all of these functions exist for other dimensionalities and types of sampler, and a full list is in Appendix C, “Built-in GLSL Variables and Functions”.

gvec4 textureProjLod(gsampler2D tex, vec2 P, float lod);gvec4 textureProjGrad(gsampler2D ...