Now that we’ve made it this far, let’s take some time to go over a few of the more advanced ways of rendering things in OpenGL.
Back in Chapter 7, Adding Detail with Textures, we learned that we can easily apply a texture by specifying a set of texture coordinates and by using a texture unit to pass in the actual texture. OpenGL ES 2.0 actually provides support for multiple texture units, with most GPUs supporting at least two of them. This can be used to blend between two textures to apply various effects. In the sample project, we use multitexturing to draw the terrain with a blend between a grassy texture at low elevations and a stony texture at higher elevations.