Debugging

Debugging WebGL applications

WebGL's error reporting mechanism involves calling getError and checking for errors. As it can be burdensome to put a getError call after every WebGL function call here is small library to help with make this easier.

https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/sdk/debug/webgl-debug.js

To use the library, download it, put it on your server and include it with

<script src="webgl-debug.js"></script>

Then you can wrap your WebGLRenderingContext in an object that checks all calls like this

ctx = WebGLDebugUtils.makeDebugContext(canvas.getContext("webgl"));

This will make any GL errors show up in your browser JavaScript console.

If you want to do something else, like throw an exception you can pass in your own error handling function.

function throwOnGLError(err, funcName, args) {
  throw WebGLDebugUtils.glEnumToString(err) + " was caused by call to" + funcName;
};

ctx = WebGLDebugUtils.makeDebugContext(canvas.getContext("webgl"), throwOnGLError);

Printing Errors and other constants

WebGL uses many constants and returns errors as numbers. It's often easier to display those numbers as strings. With that in mind you can call WebGLDebugUtils.glEnumToString to convert a WebGL constant to a string.

Example:

WebGLDebugUtil.init(ctx);
alert(WebGLDebugUtil.glEnumToString(ctx.getError()));