## Animating a surface with vertex displacement

A straightforward way to leverage shaders for animation is to simply transform the vertices within the vertex shader based on some time-dependent function. The OpenGL application supplies static geometry, and the vertex shader modifies the geometry using the current time (supplied as a uniform variable). This moves the computation of the vertex position from the CPU to the GPU, and leverages whatever parallelism the graphics driver makes available.

In this example, we'll create a waving surface by transforming the vertices of a tessellated quad based on a sine wave. We'll send down the pipeline a set of triangles that make up a flat surface in the *x*-*z* plane. In the vertex shader, we'll transform the *y* coordinate of each vertex based on a time-dependent sine function, and compute the normal vector of the transformed vertex. The following image shows the desired result (you'll have to imagine that the waves are travelling across the surface from...