index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>04_WebGL动画</title>
<script src="sylvester.js"></script>
<script src="glUtils.js"></script>
<script src="index.js"></script>
</head>
<body onload="start()">
<canvas id="glCanvas" width="640" height="480"></canvas>
<script id="shader-fs" type="x-shader/x-fragment">
varying lowp vec4 vColor;
void main(void) {
gl_FragColor = vColor;
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
attribute vec4 aVertexColor;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying lowp vec4 vColor;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vColor = aVertexColor;
}
</script>
</body>
</html>
index.js
var canvas;
var gl;
var squareVerticesBuffer;
var squareVerticesColorBuffer;
var squareRotation = 0.0;
var squareXOffset = 0.0;
var squareYOffset = 0.0;
var squareZOffset = 0.0;
var lastSquareUpdateTime = 0;
var xIncValue = 0.2;
var yIncValue = -0.4;
var zIncValue = 0.3;
var mvMatrix;
var shaderProgram;
var vertexPositionAttribute;
var vertexColorAttribute;
var perspectiveMatrix;
//
// start
//
// Called when the canvas is created to get the ball rolling.
//
function start() {
canvas = document.getElementById("glCanvas");
initWebGL(canvas); // Initialize the GL context
// Only continue if WebGL is available and working
if (gl) {
gl.clearColor(0.0, 0.0, 0.0, 1.0); // Clear to black, fully opaque
gl.clearDepth(1.0); // Clear everything
gl.enable(gl.DEPTH_TEST); // Enable depth testing
gl.depthFunc(gl.LEQUAL); // Near things obscure far things
// Initialize the shaders; this is where all the lighting for the
// vertices and so forth is established.
initShaders();
// Here's where we call the routine that builds all the objects
// we'll be drawing.
initBuffers();
// Set up to draw the scene periodically.
setInterval(drawScene, 15);
}
}
//
// initWebGL
//
// Initialize WebGL, returning the GL context or null if
// WebGL isn't available or could not be initialized.
//
function initWebGL() {
gl = null;
try {
gl = canvas.getContext("experimental-webgl");
}
catch (e) {
}
// If we don't have a GL context, give up now
if (!gl) {
alert("Unable to initialize WebGL. Your browser may not support it.");
}
}
//
// initBuffers
//
// Initialize the buffers we'll need. For this demo, we just have
// one object -- a simple two-dimensional square.
//
function initBuffers() {
// Create a buffer for the square's vertices.
squareVerticesBuffer = gl.createBuffer();
// Select the squareVerticesBuffer as the one to apply vertex
// operations to from here out.
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesBuffer);
// Now create an array of vertices for the square. Note that the Z
// coordinate is always 0 here.
var vertices = [
1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, -1.0, 0.0
];
// Now pass the list of vertices into WebGL to build the shape. We
// do this by creating a Float32Array from the JavaScript array,
// then use it to fill the current vertex buffer.
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
// Now set up the colors for the vertices
var colors = [
1.0, 1.0, 1.0, 1.0, // white
1.0, 0.0, 0.0, 1.0, // red
0.0, 1.0, 0.0, 1.0, // green
0.0, 0.0, 1.0, 1.0 // blue
];
squareVerticesColorBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesColorBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
}
//
// drawScene
//
// Draw the scene.
//
function drawScene() {
// Clear the canvas before we start drawing on it.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Establish the perspective with which we want to view the
// scene. Our field of view is 45 degrees, with a width/height
// ratio of 640:480, and we only want to see objects between 0.1 units
// and 100 units away from the camera.
perspectiveMatrix = makePerspective(45, 640.0 / 480.0, 0.1, 100.0);
// Set the drawing position to the "identity" point, which is
// the center of the scene.
loadIdentity();
// Now move the drawing position a bit to where we want to start
// drawing the square.
mvTranslate([-0.0, 0.0, -6.0]);
// Save the current matrix, then rotate before we draw.
mvPushMatrix();
mvRotate(squareRotation, [1, 0, 1]);
mvTranslate([squareXOffset, squareYOffset, squareZOffset]);
// Draw the square by binding the array buffer to the square's vertices
// array, setting attributes, and pushing it to GL.
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesBuffer);
gl.vertexAttribPointer(vertexPositionAttribute, 3, gl.FLOAT, false, 0, 0);
// Set the colors attribute for the vertices.
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesColorBuffer);
gl.vertexAttribPointer(vertexColorAttribute, 4, gl.FLOAT, false, 0, 0);
// Draw the square.
setMatrixUniforms();
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
// Restore the original matrix
mvPopMatrix();
// Update the rotation for the next draw, if it's time to do so.
var currentTime = (new Date).getTime();
if (lastSquareUpdateTime) {
var delta = currentTime - lastSquareUpdateTime;
squareRotation += (30 * delta) / 1000.0;
squareXOffset += xIncValue * ((30 * delta) / 1000.0);
squareYOffset += yIncValue * ((30 * delta) / 1000.0);
squareZOffset += zIncValue * ((30 * delta) / 1000.0);
if (Math.abs(squareYOffset) > 2.5) {
xIncValue = -xIncValue;
yIncValue = -yIncValue;
zIncValue = -zIncValue;
}
}
lastSquareUpdateTime = currentTime;
}
//
// initShaders
//
// Initialize the shaders, so WebGL knows how to light our scene.
//
function initShaders() {
var fragmentShader = getShader(gl, "shader-fs");
var vertexShader = getShader(gl, "shader-vs");
// Create the shader program
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
// If creating the shader program failed, alert
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
alert("Unable to initialize the shader program: " + gl.getProgramInfoLog(shader));
}
gl.useProgram(shaderProgram);
vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
gl.enableVertexAttribArray(vertexPositionAttribute);
vertexColorAttribute = gl.getAttribLocation(shaderProgram, "aVertexColor");
gl.enableVertexAttribArray(vertexColorAttribute);
}
//
// getShader
//
// Loads a shader program by scouring the current document,
// looking for a script with the specified ID.
//
function getShader(gl, id) {
var shaderScript = document.getElementById(id);
// Didn't find an element with the specified ID; abort.
if (!shaderScript) {
return null;
}
// Walk through the source element's children, building the
// shader source string.
var theSource = "";
var currentChild = shaderScript.firstChild;
while (currentChild) {
if (currentChild.nodeType == 3) {
theSource += currentChild.textContent;
}
currentChild = currentChild.nextSibling;
}
// Now figure out what type of shader script we have,
// based on its MIME type.
var shader;
if (shaderScript.type == "x-shader/x-fragment") {
shader = gl.createShader(gl.FRAGMENT_SHADER);
} else if (shaderScript.type == "x-shader/x-vertex") {
shader = gl.createShader(gl.VERTEX_SHADER);
} else {
return null; // Unknown shader type
}
// Send the source to the shader object
gl.shaderSource(shader, theSource);
// Compile the shader program
gl.compileShader(shader);
// See if it compiled successfully
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert("An error occurred compiling the shaders: " + gl.getShaderInfoLog(shader));
return null;
}
return shader;
}
//
// Matrix utility functions
//
function loadIdentity() {
mvMatrix = Matrix.I(4);
}
function multMatrix(m) {
mvMatrix = mvMatrix.x(m);
}
function mvTranslate(v) {
multMatrix(Matrix.Translation($V([v[0], v[1], v[2]])).ensure4x4());
}
function setMatrixUniforms() {
var pUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
gl.uniformMatrix4fv(pUniform, false, new Float32Array(perspectiveMatrix.flatten()));
var mvUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
gl.uniformMatrix4fv(mvUniform, false, new Float32Array(mvMatrix.flatten()));
}
var mvMatrixStack = [];
function mvPushMatrix(m) {
if (m) {
mvMatrixStack.push(m.dup());
mvMatrix = m.dup();
} else {
mvMatrixStack.push(mvMatrix.dup());
}
}
function mvPopMatrix() {
if (!mvMatrixStack.length) {
throw ("Can't pop from an empty matrix stack.");
}
mvMatrix = mvMatrixStack.pop();
return mvMatrix;
}
function mvRotate(angle, v) {
var inRadians = angle * Math.PI / 180.0;
var m = Matrix.Rotation(inRadians, $V([v[0], v[1], v[2]])).ensure4x4();
multMatrix(m);
}