mono/MonoGame — pull request #1117 by RayBatts (2012-12-28 02:18:22+00:00)
Title: Switching GL float precision from highp to mediump.

There's enough discussion on this topic in https://github.com/mono/MonoGame/issues/1090, https://github.com/mono/MonoGame/pull/1030, and https://github.com/mono/MonoGame/issues/909 so I'll refer to those.

Long story short, shader precision for our floats was defaulting to highp, which is a full 16 bits. Lowering this to 10 bits offers a pretty large performance win when drawing sprites.

Should developers really want high precision floats in their shaders, they're more than free to recompile for highp. Defaulting to mediump returns us closer to the performance people desired from MonoGame 2.0 and GLES 1.1.