mrdoob/three.js — pull request #1602 by jfeldste (2012-03-28 20:16:42+00:00)
Title: Added precision qualifiers to resolve shader compilation errors on mobile devices.

You guys recently added "precision mediump float" to your fragment shaders. This caused several shaders to no longer compile on mobile devices. The reason is that highp is still intrinsically being specified for several vertex shader uniforms which are now also being used in the fragment shader as medium. This conflict causes the compilation issue.

There are essentially 3 possible solutions to this problem:

1. Change the fragment shader precision back to highp which was likely done for a good reason.

2. Change the vertex shader precision for the uniforms in question to mediump.

3. Change the fragment shader precision for the uniforms in question to highp. (this is what is being done in the attached code fragments)