OpenGL 4 Shading Language Cookbook - Third Edition

Using sampler objects

Sampler objects were introduced in OpenGL 3.3 and provide a convenient way to specify the sampling parameters for a GLSL sampler variable. The traditional way to specify the parameters for a texture is to specify them using glTexParameter, typically at the time that the texture is defined. The parameters define the sampling state (sampling mode, wrapping and clamping rules, and so on) for the associated texture. This essentially combines the texture and its sampling state into a single object. If we wanted to sample from a single texture in more than one way (with and without linear filtering for example), we'd have two choices. We would either need to modify the texture's sampling state, or use two copies of the same ...