02、添加颜色

创建日期：2024-06-21
更新日期：2025-01-12
<!DOCTYPE html>

<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>02_添加颜色</title>

    <script type="text/javascript" src="Oak3D_v_0_5.js"></script>

    <script id="shader-fs" type="x-shader/x-fragment">

        precision mediump float;

        varying 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 vec4 vColor;

        void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vColor = aVertexColor;
        }
    </script>
    <script type="text/javascript">

        var gl;

        function initGL(canvas) {
            try {
                gl = canvas.getContext("experimental-webgl");
                gl.viewportWidth = canvas.width;
                gl.viewportHeight = canvas.height;
            } catch (e) {
            }
            if (!gl) {
                alert("Could not initialise WebGL, sorry :-(");
            }
        }

        function getShader(gl, id) {
            var shaderScript = document.getElementById(id);
            if (!shaderScript) {
                return null;
            }

            var str = "";
            var k = shaderScript.firstChild;
            while (k) {
                if (k.nodeType == 3) {
                    str += k.textContent;
                }
                k = k.nextSibling;
            }

            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;
            }

            gl.shaderSource(shader, str);
            gl.compileShader(shader);

            if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
                alert(gl.getShaderInfoLog(shader));
                return null;
            }

            return shader;
        }

        var shaderProgram;

        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("Could not initialise shaders");
            }

            gl.useProgram(shaderProgram);

            shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
            gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

            shaderProgram.vertexColorAttribute = gl.getAttribLocation(shaderProgram, "aVertexColor");
            gl.enableVertexAttribArray(shaderProgram.vertexColorAttribute);

            shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
            shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
        }

        var mvMatrix;
        var pMatrix;

        function setMatrixUniforms() {
            gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix.toArray());
            gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix.toArray());
        }

        var triangleVertexPositionBuffer;
        var triangleVertexColorBuffer;
        var squareVertexPositionBuffer;
        var squareVertexColorBuffer;

        function initBuffers() {
            triangleVertexPositionBuffer = gl.createBuffer();
            gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
            var 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);
            triangleVertexPositionBuffer.itemSize = 3;
            triangleVertexPositionBuffer.numItems = 3;

            triangleVertexColorBuffer = gl.createBuffer();
            gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexColorBuffer);
            var 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);
            triangleVertexColorBuffer.itemSize = 4;
            triangleVertexColorBuffer.numItems = 3;

            squareVertexPositionBuffer = gl.createBuffer();
            gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
            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
            ];
            gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
            squareVertexPositionBuffer.itemSize = 3;
            squareVertexPositionBuffer.numItems = 4;

            squareVertexColorBuffer = gl.createBuffer();
            gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexColorBuffer);
            colors = []
            for (var i = 0; i < 4; i++) {
                colors = colors.concat([0.5, 0.5, 1.0, 1.0]);
            }
            gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
            squareVertexColorBuffer.itemSize = 4;
            squareVertexColorBuffer.numItems = 4;
        }

        function drawScene() {
            gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
            gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

            pMatrix = okMat4Proj(45.0, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0);

            mvMatrix = okMat4Trans(-1.5, 0.0, -7.0);

            gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
            gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, triangleVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

            gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexColorBuffer);
            gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, triangleVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

            setMatrixUniforms();
            gl.drawArrays(gl.TRIANGLES, 0, triangleVertexPositionBuffer.numItems);

            mvMatrix = okMat4Trans(1.5, 0.0, -7.0);
            gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
            gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

            gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexColorBuffer);
            gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, squareVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

            setMatrixUniforms();
            gl.drawArrays(gl.TRIANGLE_STRIP, 0, squareVertexPositionBuffer.numItems);
        }

        function webGLStart() {
            var canvas = document.getElementById("lesson02-canvas");
            initGL(canvas);
            initShaders();
            initBuffers();

            gl.clearColor(0.0, 0.0, 0.0, 1.0);
            gl.enable(gl.DEPTH_TEST);

            drawScene();
        }

    </script>
</head>

<body onLoad="webGLStart();">
    <canvas id="lesson02-canvas" style="border: none;" width="500" height="500"></canvas>
</body>
</html>
简介

一个来自三线小城市的程序员开发经验总结。
02、添加颜色

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