ARM Community: Multimedia - ARM Community

As graphics processor hardware now supports a number of different floating point data formats, it is important to understand how to select an appropriate format for your calculations, and why the choice is important. Even the simplest of operations benefit greatly from a little thought. Here is an instructive example that we recently came across.

Animating Shaders

If you are creating an animated shader in OpenGL ES, you will need to tell it the time. The obvious way to do this is to create a uniform variable called, let’s say, animation_time, and use it to modify some aspect of the object we are drawing, such as its color, position, or texture. Let us look at some complications that can occur.

Here is a very simple animated pixel shader that uses the time to pulse a red light repeatedly:

The fract function returns the fractional part of the animation_time value, which gives us a sawtooth-like ramp over time. This is placed in the red component of the fragment color, so that the object appears to be repeatedly pulsing red.

We pass ...