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webgl_cube.html
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webgl_cube.html
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<!doctype html>
<html>
<head>
<title>WebGL Textured Cube Demo</title>
<script type="text/javascript">
/* global Image, alert, requestAnimationFrame */
var canvas
var gl
var cubePositionBuffer
var cubeUvBuffer
var cubeElementsBuffers
var cubeTexture
var shaderProgram
var cubePositionAttribute
var cubeUvAttribute
var projectionUniformLocation
var viewUniformLocation
var tick
function start () {
canvas = document.getElementById('glcanvas')
tick = 0
initWebGL(canvas)
if (gl) {
gl.clearColor(0.0, 0.0, 0.0, 1.0)
gl.enable(gl.DEPTH_TEST)
gl.enable(gl.CULL_FACE)
initShaders()
initBuffers()
initTextures()
// start RAF
requestAnimationFrame(drawScene)
}
}
function initWebGL () {
try {
gl = canvas.getContext('experimental-webgl')
} catch (e) {
}
if (!gl) {
alert('Unable to initialize WebGL. Your browser may not support it.')
}
}
function initBuffers () {
cubePositionBuffer = gl.createBuffer()
gl.bindBuffer(gl.ARRAY_BUFFER, cubePositionBuffer)
var cubePosition = [
// positive z face.
-0.5, +0.5, +0.5,
+0.5, +0.5, +0.5,
+0.5, -0.5, +0.5,
-0.5, -0.5, +0.5,
// positive x face
+0.5, +0.5, +0.5,
+0.5, +0.5, -0.5,
+0.5, -0.5, -0.5,
+0.5, -0.5, +0.5,
// negative z face
+0.5, +0.5, -0.5,
-0.5, +0.5, -0.5,
-0.5, -0.5, -0.5,
+0.5, -0.5, -0.5,
// negative x face.
-0.5, +0.5, -0.5,
-0.5, +0.5, +0.5,
-0.5, -0.5, +0.5,
-0.5, -0.5, -0.5,
// top face
-0.5, +0.5, -0.5,
+0.5, +0.5, -0.5,
+0.5, +0.5, +0.5,
-0.5, +0.5, +0.5,
// bottom face
-0.5, -0.5, -0.5,
+0.5, -0.5, -0.5,
+0.5, -0.5, +0.5,
-0.5, -0.5, +0.5
]
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(cubePosition), gl.STATIC_DRAW)
cubeUvBuffer = gl.createBuffer()
gl.bindBuffer(gl.ARRAY_BUFFER, cubeUvBuffer)
var cubeUv = [
// positive z face.
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// positive x face.
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// negative z face.
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// negative x face.
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// top face
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// bottom face
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0
]
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(cubeUv), gl.STATIC_DRAW)
cubeElementsBuffers = gl.createBuffer()
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeElementsBuffers)
var cubeElements = [
// positive z face.
2, 1, 0,
2, 0, 3,
// positive x face.
6, 5, 4,
6, 4, 7,
// negative z face.
10, 9, 8,
10, 8, 11,
// negative x face.
14, 13, 12,
14, 12, 15,
// top face.
18, 17, 16,
18, 16, 19,
// bottom face
20, 21, 22,
23, 20, 22
]
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeElements), gl.STATIC_DRAW)
}
function initTextures () {
cubeTexture = gl.createTexture()
var cubeImage = new Image()
cubeImage.onload = function () {
gl.bindTexture(gl.TEXTURE_2D, cubeTexture)
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, cubeImage)
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
}
cubeImage.src = 'assets/peppers.png'
}
function drawScene () {
tick++
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
// bind buffers.
gl.bindBuffer(gl.ARRAY_BUFFER, cubePositionBuffer)
gl.vertexAttribPointer(cubePositionAttribute, 3, gl.FLOAT, false, 0, 0)
gl.bindBuffer(gl.ARRAY_BUFFER, cubeUvBuffer)
gl.vertexAttribPointer(cubeUvAttribute, 2, gl.FLOAT, false, 0, 0)
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeElementsBuffers)
// set texture.
gl.activeTexture(gl.TEXTURE0)
gl.bindTexture(gl.TEXTURE_2D, cubeTexture)
// set uniforms
gl.uniform1i(gl.getUniformLocation(shaderProgram, 'tex'), 0)
const t = 0.01 * tick
var perspectiveMatrix = perspective(45, 640.0 / 480.0, 0.1, 100.0)
gl.uniformMatrix4fv(projectionUniformLocation, false, new Float32Array(perspectiveMatrix))
gl.uniformMatrix4fv(viewUniformLocation, false, new Float32Array(
lookAt(
[5 * Math.cos(t), 2.5 * Math.sin(t), 5 * Math.sin(t)],
[0, 0.0, 0],
[0, 1, 0])))
gl.drawElements(gl.TRIANGLES, 36, gl.UNSIGNED_SHORT, 0)
requestAnimationFrame(drawScene)
}
function initShaders () {
var fragmentShader = getShader(gl, 'shader-fs')
var vertexShader = getShader(gl, 'shader-vs')
shaderProgram = gl.createProgram()
gl.attachShader(shaderProgram, vertexShader)
gl.attachShader(shaderProgram, fragmentShader)
gl.linkProgram(shaderProgram)
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram))
}
gl.useProgram(shaderProgram)
cubePositionAttribute = gl.getAttribLocation(shaderProgram, 'position')
gl.enableVertexAttribArray(cubePositionAttribute)
cubeUvAttribute = gl.getAttribLocation(shaderProgram, 'uv')
gl.enableVertexAttribArray(cubeUvAttribute)
projectionUniformLocation = gl.getUniformLocation(shaderProgram, 'projection')
viewUniformLocation = gl.getUniformLocation(shaderProgram, 'view')
}
function getShader (gl, id) {
var e = document.getElementById(id)
if (!e) {
return null
}
var sourceCode = e.firstChild.textContent
var shader
if (e.type === 'x-shader/x-fragment') {
shader = gl.createShader(gl.FRAGMENT_SHADER)
} else if (e.type === 'x-shader/x-vertex') {
shader = gl.createShader(gl.VERTEX_SHADER)
} else {
return null
}
gl.shaderSource(shader, sourceCode)
gl.compileShader(shader)
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader))
return null
}
return shader
}
// Taken from gl-mat4
// https://github.com/stackgl/gl-mat4/blob/master/lookAt.js
function lookAt (eye, center, up) {
var x0, x1, x2, y0, y1, y2, z0, z1, z2, len
var eyex = eye[0]
var eyey = eye[1]
var eyez = eye[2]
var upx = up[0]
var upy = up[1]
var upz = up[2]
var centerx = center[0]
var centery = center[1]
var centerz = center[2]
z0 = eyex - centerx
z1 = eyey - centery
z2 = eyez - centerz
len = 1 / Math.sqrt(z0 * z0 + z1 * z1 + z2 * z2)
z0 *= len
z1 *= len
z2 *= len
x0 = upy * z2 - upz * z1
x1 = upz * z0 - upx * z2
x2 = upx * z1 - upy * z0
len = Math.sqrt(x0 * x0 + x1 * x1 + x2 * x2)
if (!len) {
x0 = 0
x1 = 0
x2 = 0
} else {
len = 1 / len
x0 *= len
x1 *= len
x2 *= len
}
y0 = z1 * x2 - z2 * x1
y1 = z2 * x0 - z0 * x2
y2 = z0 * x1 - z1 * x0
len = Math.sqrt(y0 * y0 + y1 * y1 + y2 * y2)
if (!len) {
y0 = 0
y1 = 0
y2 = 0
} else {
len = 1 / len
y0 *= len
y1 *= len
y2 *= len
}
return [
x0, y0, z0, 0,
x1, y1, z1, 0,
x2, y2, z2, 0,
-(x0 * eyex + x1 * eyey + x2 * eyez),
-(y0 * eyex + y1 * eyey + y2 * eyez),
-(z0 * eyex + z1 * eyey + z2 * eyez),
1
]
}
// Taken from gl-mat4
// https://github.com/stackgl/gl-mat4/blob/master/perspective.js
function perspective (fovy, aspect, near, far) {
var f = 1.0 / Math.tan(fovy / 2)
var nf = 1 / (near - far)
return [
f / aspect, 0.0, 0.0, 0.0,
0.0, f, 0.0, 0.0,
0.0, 0.0, (far + near) * nf, -1.0,
0.0, 0.0, (2 * far * near) * nf, 0.0
]
}
</script>
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec2 vUv;
uniform sampler2D tex;
void main () {
gl_FragColor = texture2D(tex,vUv);
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
precision mediump float;
attribute vec3 position;
attribute vec2 uv;
varying vec2 vUv;
uniform mat4 projection, view;
void main() {
vUv = uv;
gl_Position = projection * view * vec4(position, 1);
}
</script>
</head>
<body onload="start()">
<canvas id="glcanvas" width="640" height="480">
Your browser doesn't appear to support the <code><canvas></code> element.
</canvas>
</body>
</html>