gistfile1.txt

	initGL = (canvas) ->
		gl = canvas.getContext 'experimental-webgl'
		gl.viewportWidth  = canvas.width
		gl.viewportHeight = canvas.height
		
		if not gl
			throw new Error "Could not initialise WebGL :("
		
		gl
	
	shaders =
		"fragment": """
			#ifdef GL_ES
			precision highp float;
			#endif
			
			varying vec4 vColor;
			
			void main(void) {
			//	gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
			//	gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
				gl_FragColor = vColor;
			}
			"""
		
		"vertex": """
			attribute vec3 aVertexPosition;
			attribute vec4 aVertexColor;
			
			uniform mat4 uMVMatrix;
			uniform mat4 uPMatrix;
			
			varying vec4 vColor;
		 
			void main(void) {
				gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
				vColor = aVertexColor;
			}
			"""
	
	getShader = (gl, type) ->
		shaderConst = (
			"fragment" : gl.FRAGMENT_SHADER
			"vertex"   : gl.VERTEX_SHADER
		)[type]
		
		shader = gl.createShader shaderConst
		gl.shaderSource shader, shaders[type]
		gl.compileShader shader
		
		if not gl.getShaderParameter shader, gl.COMPILE_STATUS
			throw new Error gl.getShaderInfoLog shader
		
		shader
	
	mvMatrix = mat4.create()
	pMatrix  = mat4.create()
	
	init = ->
		canvas = document.getElementById 'canvas'
		gl = initGL canvas
		
		# ------ Initialise shaders ------
		fragmentShader = getShader gl, "fragment"
		vertexShader   = getShader gl, "vertex"
		
		prog = gl.createProgram()
		gl.attachShader prog, vertexShader
		gl.attachShader prog, fragmentShader
		gl.linkProgram prog
		
		if not gl.getProgramParameter prog, gl.LINK_STATUS
			throw new Error "Could not initialise shaders"
		
		gl.useProgram prog
		
		prog.vertexPositionAttribute = gl.getAttribLocation prog, "aVertexPosition"
		gl.enableVertexAttribArray prog.vertexPositionAttribute
		
		prog.vertexColorAttribute = gl.getAttribLocation prog, "aVertexColor"
		gl.enableVertexAttribArray prog.vertexColorAttribute
		
		prog.pMatrixUniform  = gl.getUniformLocation prog, "uPMatrix"
		prog.mvMatrixUniform = gl.getUniformLocation prog, "uMVMatrix"
		
		shaderProg = prog
		
		#shaderProg = initShaders gl
		
		# ------ Create buffers ------
		# --- Triangle ---
		trianglePosBuf = gl.createBuffer()
		gl.bindBuffer gl.ARRAY_BUFFER, trianglePosBuf
		vertices = [
			 0.0,  1.0,  0.0
			-1.0, -1.0,  0.0
			 1.0, -1.0,  0.0
		]
		
		gl.bufferData gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW
		
		# --- Triangle (color) ---
		triangleColorBuf = gl.createBuffer()
		gl.bindBuffer gl.ARRAY_BUFFER, triangleColorBuf
		colors = [
			1.0, 0.0, 0.0, 1.0
			0.0, 1.0, 0.0, 1.0
			0.0, 0.0, 1.0, 1.0
		]
		
		gl.bufferData gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW
		
		# Assign the buffers
		buffers = triangle:
			position : trianglePosBuf
			color    : triangleColorBuf
			length   : 3
		
		# ------ Prepare rendering ------
		gl.clearColor 0.0, 0.0, 0.0, 1.0
		gl.enable gl.DEPTH_TEST
		
		# ------ Render scene ------
		gl.viewport 0, 0, gl.viewportWidth, gl.viewportHeight
		gl.clear gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT
		
		mat4.perspective 45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix
		mat4.identity mvMatrix
		
		setMatrixUniforms = ->
			gl.uniformMatrix4fv shaderProg.pMatrixUniform,  false, pMatrix
			gl.uniformMatrix4fv shaderProg.mvMatrixUniform, false, mvMatrix
		
		# Draw triangle
		# Note: 3 & 4 is the width of the matrix in the buffer.
		mat4.translate mvMatrix, [-1.5, 0.0, -7.0]
		gl.bindBuffer gl.ARRAY_BUFFER, buffers.triangle.position
		gl.vertexAttribPointer shaderProg.vertexPositionAttribute,
				3, gl.FLOAT, false, 0, 0
		
		gl.bindBuffer gl.ARRAY_BUFFER, buffers.triangle.color
		gl.vertexAttribPointer shaderProg.vertexColorAttribute,
				4, gl.FLOAT, false, 0, 0
		
		setMatrixUniforms()
		gl.drawArrays gl.TRIANGLES, 0, buffers.triangle.length
	
	window.addEventListener 'load', init, false