With the the increasing popularity of WebGL comes the need for javascript libraries that handle matrix and vector operations. glMatrix is designed to handle those operations at stupidly fast speeds!
Most matrix operations share a similar format:
mat4.operation(srcMatrix, otherOperands, destMatrix (optional));
For all functions following this format the operation will be applied to the values in srcMatrix and the result will be written into destMatrix, which will also be returned. If destMatrix is not specified the result will be written into srcMatrix, if destMatrix is specified srcMatrix will not be altered.
Any 4x4 matrix functions expect sequences at least 16 elements in length as inputs when taking a matrix.
Documentation for the individual functions can be found here
Creating a perspective matrix
var persp = mat4.create();
mat4.perspective(45, 4/3, 1, 100, persp);
Performing multiple transforms on a matrix
var modelView = mat4.create();
mat4.identity(modelView); // Set to identity
mat4.translate(modelView, [0, 0, -10]); // Translate back 10 units
mat4.rotate(modelView, Math.PI/2, [0, 1, 0]); // Rotate 90 degrees around the Y axis
mat4.scale(modelView, [2, 2, 2]); // Scale by 200%
Matricies created with glMatrix don't need to undergo any transformation to be used with WebGL. They can be passed directly
gl.uniformMatrix4fv(modelViewUniform, false, modelView);
Updating a destination matrix
var modelViewPersp = mat4.create();
mat4.multiply(modelView, persp, modelViewPersp); // Sets modelViewPersp to modelView * persp
Tranforming a point
var cameraPos = [0, 0, 0];
var newPos = [0, 0, 0];
mat4.multiplyVec3(modelView, cameraPos); // Result is written into cameraPos
mat4.multiplyVec3(modelView, cameraPos, newPos); // Result is written into newPos