webgl学习笔记三-平移旋转缩放

写在前面

建议先阅读下前面我的两篇文章。

webgl学习笔记一-绘图单点

webgl学习笔记二-绘图多点

平移

1、关键点说明

顶点着色器需要加上 uniform vec4 u_Translation, 存储平移的坐标矢量。
顶点坐标位置： gl_Position = a_Position + u_Translation
平移API ： gl.uniform4f(u_Translation, Tx, Ty, Tz, 0.0);

2、demo

html

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>Title</title>

</head>

<body>

<canvas id="canvas" width="200px" height="200px"></canvas>

</body>

</html>

JavaScript



<script>

    function main() {

        //顶点着色器程序

        var VSHADER_SOURCE =

            'attribute vec4 a_Position;\n' +

            'uniform vec4 u_Translation;\n' +

            'void main() {\n' +

            '  gl_Position = a_Position + u_Translation;\n' +

            '}\n';

        //片元着色器

        var FSHADER_SOURCE =

            'void main() {\n' +

            '  gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +

            '}\n';

        //获取canvas元素

        var canvas = document.getElementById('canvas');

        //获取绘制二维上下文

        var gl = canvas.getContext('webgl');

        if (!gl) {

            console.log("Failed");

            return;

        }

        //编译着色器

        var vertShader = gl.createShader(gl.VERTEX_SHADER);

        gl.shaderSource(vertShader, VSHADER_SOURCE);

        gl.compileShader(vertShader);

        var fragShader = gl.createShader(gl.FRAGMENT_SHADER);

        gl.shaderSource(fragShader, FSHADER_SOURCE);

        gl.compileShader(fragShader);

        //合并程序

        var shaderProgram = gl.createProgram();

        gl.attachShader(shaderProgram, vertShader);

        gl.attachShader(shaderProgram, fragShader);

        gl.linkProgram(shaderProgram);

        gl.useProgram(shaderProgram);

        //获取坐标点

        var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');

        if (a_Position < 0) {

            console.log('Failed to get the storage location of a_Position');

            return;

        }

        var n = initBuffers(gl, shaderProgram);

        if (n < 0) {

            console.log('Failed to set the positions');

            return;

        }

        // 清除指定<画布>的颜色

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

        // 清空 <canvas>

        gl.clear(gl.COLOR_BUFFER_BIT);

        gl.drawArrays(gl.TRIANGLES, 0, n);

    }

    function opt(gl, shaderProgram) {

        var Tx = 0.5, Ty = 0.5, Tz = 0.0;

        var u_Translation = gl.getUniformLocation(shaderProgram, 'u_Translation');

        if (!u_Translation) {

            console.log('Failed to get the storage location of u_Translation');

            return;

        }

        gl.uniform4f(u_Translation, Tx, Ty, Tz, 0.0);

    }

    function initBuffers(gl, shaderProgram) {

        var vertices = new Float32Array([

            0, 0.5,   -0.5, -0.5,   0.5, -0.5

        ]);

        var n = 3;//点的个数

        //创建缓冲区对象

        var vertexBuffer = gl.createBuffer();

        if (!vertexBuffer) {

            console.log("Failed to create the butter object");

            return -1;

        }

        //将缓冲区对象绑定到目标

        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

        //向缓冲区写入数据

        gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

        //获取坐标点

        var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');

        //将缓冲区对象分配给a_Position变量

        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

        //连接a_Position变量与分配给它的缓冲区对象

        gl.enableVertexAttribArray(a_Position);

        return n;

    }

    main();

</script>

旋转

1、关键点说明

坐标P（x,y,z） , 绕Z轴旋转β角度变成 p1（x1, y1, z1）

则根据数据三角函数公式可得：

x1 = xcosβ - ysinβ

y1 = xsinβ + ycosβ

z1=z

顶点着色器需要加上 uniform float u_CosB, u_SinB 存储旋转角度。
顶点坐标位置：
- gl_Position.x = a_Position.x * u_CosB - a_Position.y * u_SinB
- gl_Position.y = a_Position.x * u_SinB + a_Position.y * u_CosB
旋转API ：
- gl.uniform1f(u_CosB, cosB)
- gl.uniform1f(u_sinB, sinB);

2、demo

JavaScript

<script>

    function main() {

        //顶点着色器程序

        var VSHADER_SOURCE =

            'attribute vec4 a_Position;\n' +

            'uniform float u_CosB, u_SinB;\n' +

            'void main() {\n' +

            '  gl_Position.x = a_Position.x * u_CosB - a_Position.y * u_SinB;\n' +

            '  gl_Position.y = a_Position.x * u_SinB + a_Position.y * u_CosB;\n' +

            '  gl_Position.z = a_Position.z;\n' +

            '  gl_Position.w = 1.0;\n' +

            '}\n';

        //片元着色器程序

        var FSHADER_SOURCE =

            'void main() {\n' +

            '  gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +

            '}\n';

        var Tx = 0.5, Ty = 0.5, Tz = 0.0;

        //获取canvas元素

        var canvas = document.getElementById('canvas');

        //获取绘制二维上下文

        var gl = canvas.getContext('webgl');

        if (!gl) {

            console.log("Failed");

            return;

        }

        //编译着色器

        var vertShader = gl.createShader(gl.VERTEX_SHADER);

        gl.shaderSource(vertShader, VSHADER_SOURCE);

        gl.compileShader(vertShader);

        var fragShader = gl.createShader(gl.FRAGMENT_SHADER);

        gl.shaderSource(fragShader, FSHADER_SOURCE);

        gl.compileShader(fragShader);

        //合并程序

        var shaderProgram = gl.createProgram();

        gl.attachShader(shaderProgram, vertShader);

        gl.attachShader(shaderProgram, fragShader);

        gl.linkProgram(shaderProgram);

        gl.useProgram(shaderProgram);

        //获取坐标点

        var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');

        if (a_Position < 0) {

            console.log('Failed to get the storage location of a_Position');

            return;

        }

        var n = initBuffers(gl, shaderProgram);

        if (n < 0) {

            console.log('Failed to set the positions');

            return;

        }

        opt(gl, shaderProgram);

        // 清除指定<画布>的颜色

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

        // 清空 <canvas>

        gl.clear(gl.COLOR_BUFFER_BIT);

        gl.drawArrays(gl.TRIANGLES, 0, n);

    }

    function opt(gl, program) {

        // 旋转角度

        var ANGLE = 90.0;

        var radian = Math.PI * ANGLE / 180.0;

        var cosB = Math.cos(radian);

        var sinB = Math.sin(radian);

        var u_CosB = gl.getUniformLocation(program, 'u_CosB');

        var u_sinB = gl.getUniformLocation(program, 'u_SinB');

        gl.uniform1f(u_CosB, cosB);

        gl.uniform1f(u_sinB, sinB);

    }

    function initBuffers(gl, shaderProgram) {

        var vertices = new Float32Array([

            0, 0.5,   -0.5, -0.5,   0.5, -0.5

        ]);

        var n = 3;//点的个数

        //创建缓冲区对象

        var vertexBuffer = gl.createBuffer();

        if (!vertexBuffer) {

            console.log("Failed to create the butter object");

            return -1;

        }

        //将缓冲区对象绑定到目标

        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

        //向缓冲区写入数据

        gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

        //获取坐标点

        var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');

        //将缓冲区对象分配给a_Position变量

        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

        //连接a_Position变量与分配给它的缓冲区对象

        gl.enableVertexAttribArray(a_Position);

        return n;

    }

    main();

</script>

缩放

1、关键点说明

顶点着色器需要加上 uniform mat4 u_xformMatrix, 存储缩放因子的坐标矢量。
顶点坐标位置： gl_Position = u_xformMatrix * a_Position
缩放API ： gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);
- u_xformMatrix ：缩放因子
- xformMatrix ：原始坐标

2、demo

JavaScript

<script>

    function main() {

        //顶点着色器程序

        var VSHADER_SOURCE =

            'attribute vec4 a_Position;\n' +

            'uniform mat4 u_xformMatrix;\n' +

            'void main() {\n' +

            '  gl_Position = u_xformMatrix * a_Position;\n' +

            '}\n';

        //片元着色器程序

        var FSHADER_SOURCE =

            'void main() {\n' +

            '  gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +

            '}\n';

        var Tx = 0.5, Ty = 0.5, Tz = 0.0;

        //获取canvas元素

        var canvas = document.getElementById('canvas');

        //获取绘制二维上下文

        var gl = canvas.getContext('webgl');

        if (!gl) {

            console.log("Failed");

            return;

        }

        //编译着色器

        var vertShader = gl.createShader(gl.VERTEX_SHADER);

        gl.shaderSource(vertShader, VSHADER_SOURCE);

        gl.compileShader(vertShader);

        var fragShader = gl.createShader(gl.FRAGMENT_SHADER);

        gl.shaderSource(fragShader, FSHADER_SOURCE);

        gl.compileShader(fragShader);

        //合并程序

        var shaderProgram = gl.createProgram();

        gl.attachShader(shaderProgram, vertShader);

        gl.attachShader(shaderProgram, fragShader);

        gl.linkProgram(shaderProgram);

        gl.useProgram(shaderProgram);

        //获取坐标点

        var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');

        if (a_Position < 0) {

            console.log('Failed to get the storage location of a_Position');

            return;

        }

        var n = initBuffers(gl, shaderProgram);

        if (n < 0) {

            console.log('Failed to set the positions');

            return;

        }

        opt(gl, shaderProgram);

        // 清除指定<画布>的颜色

        gl.clearColor(0, 0, 0, 1);

        // 清空 <canvas>

        gl.clear(gl.COLOR_BUFFER_BIT);

        // Draw the rectangle

        gl.drawArrays(gl.TRIANGLES, 0, n);

    }

    // 缩放

    function opt(gl, program) {

        // 缩放因子

        var Sx = 1.0, Sy = 1.5, Sz = 1.0;

        var xformMatrix = new Float32Array([

            Sx,   0.0,  0.0,  0.0,

            0.0,  Sy,   0.0,  0.0,

            0.0,  0.0,  Sz,   0.0,

            0.0,  0.0,  0.0,  1.0

        ]);

        var u_xformMatrix = gl.getUniformLocation(program, 'u_xformMatrix');

        gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);

    }

    // 构建缓冲区

    function initBuffers(gl, shaderProgram) {

        var vertices = new Float32Array([

            0, 0.5,   -0.5, -0.5,   0.5, -0.5

        ]);

        var n = 3;//点的个数

        //创建缓冲区对象

        var vertexBuffer = gl.createBuffer();

        if (!vertexBuffer) {

            console.log("Failed to create the butter object");

            return -1;

        }

        //将缓冲区对象绑定到目标

        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

        //向缓冲区写入数据

        gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

        //获取坐标点

        var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');

        //将缓冲区对象分配给a_Position变量

        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

        //连接a_Position变量与分配给它的缓冲区对象

        gl.enableVertexAttribArray(a_Position);

        return n;

    }

    // 主方法调用

    main();

</script>

写在最后

新博客

秒客网

webgl学习笔记三-平移旋转缩放

1、关键点说明

2、demo

1、关键点说明

2、demo

1、关键点说明

2、demo

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