What does `precision mediump float` mean?

javascript opengl-es webgl terminology fragment-shader
Hard Rain picture Hard Rain · Dec 8, 2012 · Viewed 35.1k times · Source

In the learningwebgl tutorial1 I've found an interesting line in the fragment shader.

precision mediump float;

I've found an article about it here, but I still can't understand what does it mean?

And if I remove this line, nothing changes. Everything is the same. So what does precision mediump float mean?

Answer

HowDoIDoComputer picture HowDoIDoComputer · Dec 8, 2012

This determines how much precision the GPU uses when calculating floats. highp is high precision, and of course more intensive than mediump (medium precision) and lowp (low precision).

Some systems do not support highp at all, which will cause code not to work at all on those systems.

On systems that DO support highp, you will see a performance hit, and should use mediump and lowp wherever possible. A good rule of thumb that I saw was:
- highp for vertex positions,
- mediump for texture coordinates,
- lowp for colors.

Hope that helps!

Related questions

How to console.log in webgl shaders?

I'm trying to understand how to simulate console.log in webgl shaders which are written in GLSL. It's easy to get error messages but I can't get how to print custom messages. Basically I want to print stuff in the …

Read More
Better Quality Text in WebGL

I am searching a method to draw better quality (arbitrary) text inside WebGL. Currently I am using bitmap font rendering on a 2D canvas and blitting them into the WebGL context. This method is described here http://delphic.me.uk/…

Read More
Three.js - skinned skeletal mesh instances, animations and blending

I'm working on a small multiplayer game which has a single skinned player mesh with many players using it. Some Background: I've tried loading via maya and blender collada export. Both seem to reference some form of animation data but …

Read More