webGL进阶（一）多重纹理效果

效果：

代码：

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>绘制多重纹理（漂浮的云）</title><script src="glMatrix-0.9.6.min.js"></script><script>let vertexstring = `attribute vec4 a_position;uniform   mat4    proj;attribute vec2 outUV;varying vec2 inUV;void main(void){gl_Position =  a_position;inUV = outUV;}`;let fragmentstring = `precision mediump float;uniform sampler2D texture;uniform sampler2D texture1;uniform float anim;varying vec2 inUV;void main(void){vec4 color1 =texture2D(texture,inUV);vec4 color2 =texture2D(texture1, vec2(inUV.x + anim, inUV.y));gl_FragColor = color1;}`;var projMat4 = mat4.create();var webgl;var uniformTexture = 0;var uniformTexture1 = 0;var uniformAnim = 0;var count = 0;var texture0;var texture1;function webglStart() {init();tick();}function tick() {requestAnimFrame(tick)draw();};function init() {initWebgl();initShader();initBuffer();}function initWebgl() {let webglDiv = document.getElementById('myCanvas');webgl = webglDiv.getContext("webgl");webgl.viewport(0, 0, webglDiv.clientWidth, webglDiv.clientHeight);mat4.ortho(0, webglDiv.clientWidth, webglDiv.clientHeight, 0, -1.0, 1.0, projMat4)}function initShader() {let vsshader = webgl.createShader(webgl.VERTEX_SHADER);let fsshader = webgl.createShader(webgl.FRAGMENT_SHADER);webgl.shaderSource(vsshader, vertexstring);webgl.shaderSource(fsshader, fragmentstring);webgl.compileShader(vsshader);webgl.compileShader(fsshader);if (!webgl.getShaderParameter(vsshader, webgl.COMPILE_STATUS)) {var err = webgl.getShaderInfoLog(vsshader);alert(err);return;}if (!webgl.getShaderParameter(fsshader, webgl.COMPILE_STATUS)) {var err = webgl.getShaderInfoLog(fsshader);alert(err);return;}let program = webgl.createProgram();webgl.attachShader(program, vsshader);webgl.attachShader(program, fsshader)webgl.linkProgram(program);webgl.useProgram(program);webgl.program = program}function initBuffer() {let arr = [-0.5, -0.5, 0, 1,      0, 0,-0.5, 0.5, 0, 1,       0, 1,0.5, 0.5, 0, 1,         1, 1,0.5, -0.5, 0, 1,        1, 0,]let index = [0, 1, 2,2, 0, 3];let pointPosition = new Float32Array(arr);let aPsotion = webgl.getAttribLocation(webgl.program, "a_position");let triangleBuffer = webgl.createBuffer();webgl.bindBuffer(webgl.ARRAY_BUFFER, triangleBuffer);webgl.bufferData(webgl.ARRAY_BUFFER, pointPosition, webgl.STATIC_DRAW);webgl.enableVertexAttribArray(aPsotion);webgl.vertexAttribPointer(aPsotion, 4, webgl.FLOAT, false, 6 * 4, 0);let uniformProj = webgl.getUniformLocation(webgl.program, "proj");webgl.uniformMatrix4fv(uniformProj, false, projMat4);attribOutUV = webgl.getAttribLocation(webgl.program, "outUV");webgl.enableVertexAttribArray(attribOutUV);webgl.vertexAttribPointer(attribOutUV, 2, webgl.FLOAT, false, 6 * 4, 4 * 4);let indexarr = new Uint8Array(index)let indexBuffer = webgl.createBuffer();webgl.bindBuffer(webgl.ELEMENT_ARRAY_BUFFER, indexBuffer);webgl.bufferData(webgl.ELEMENT_ARRAY_BUFFER, indexarr, webgl.STATIC_DRAW);uniformTexture = webgl.getUniformLocation(webgl.program, "texture");uniformTexture1 = webgl.getUniformLocation(webgl.program, "texture1");texture1 = initTexture("fog.png");texture0 = initTexture("山水图像纹理映射.png");}function handleLoadedTexture(texture) {webgl.bindTexture(webgl.TEXTURE_2D, texture);webgl.pixelStorei(webgl.UNPACK_FLIP_Y_WEBGL,666);webgl.texImage2D(webgl.TEXTURE_2D, 0, webgl.RGBA, webgl.RGBA, webgl.UNSIGNED_BYTE, texture.image);webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_MAG_FILTER, webgl.LINEAR);webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_MIN_FILTER, webgl.LINEAR);webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_WRAP_S, webgl.CLAMP_TO_EDGE);webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_WRAP_T, webgl.CLAMP_TO_EDGE);}function initTexture(imageFile, num) {let textureHandle = webgl.createTexture();textureHandle.image = new Image();textureHandle.image.src = imageFile;textureHandle.image.onload = function () {handleLoadedTexture(textureHandle, num)}return textureHandle;}function draw() {webgl.clearColor(0.0, 1.0, 0.0, 1.0);webgl.clear(webgl.COLOR_BUFFER_BIT | webgl.DEPTH_BUFFER_BIT);webgl.enable(webgl.DEPTH_TEST);//纹理变动uniformAnim = webgl.getUniformLocation(webgl.program, "anim");count = count + 0.01;webgl.uniform1f(uniformAnim, count);webgl.activeTexture(webgl.TEXTURE0);webgl.bindTexture(webgl.TEXTURE_2D, texture0);webgl.uniform1i(uniformTexture, 0);webgl.activeTexture(webgl.TEXTURE1);webgl.bindTexture(webgl.TEXTURE_2D, texture1);webgl.uniform1i(uniformTexture1, 1);webgl.drawElements(webgl.TRIANGLES, 6, webgl.UNSIGNED_BYTE, 0);}window.requestAnimFrame = (function () {return window.requestAnimationFrame ||window.webkitRequestAnimationFrame ||window.mozRequestAnimationFrame ||window.oRequestAnimationFrame ||window.msRequestAnimationFrame ||function (callback, element) {window.setTimeout(callback, 1000 / 60);};})();</script>
</head><body onload="webglStart()"><canvas id='myCanvas' width="1024" height='1000'></canvas>
</body></html>