WebGL 3D(三角形的矩陣變換[平移、旋轉(zhuǎn)、縮放])

三角形平移

image.png
1、公式實現(xiàn)
<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            var VSHADER_SOURCE = 
                    'attribute vec4 a_Position;\n'+
                    'uniform vec4 u_Translation;\n'+
                    'void main(){\n'+
                        'gl_Position = a_Position + u_Translation;\n'+
                    '}\n';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //在x,y,z方向上平移的距離
                var Tx = 0.5, Ty = 0.5, Tz = 0.5;
                var u_Translation = gl.getUniformLocation(program, 'u_Translation');
                gl.uniform4f(u_Translation, Tx, Ty, Tz, 0.0);
                
                var n = initVertexBuffers(gl);
                if(n < 0){
                    console.log('Failed to set positions of vertices');
                    return;
                }

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

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
2、矩陣實現(xiàn)
<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            var VSHADER_SOURCE = 
                    'attribute vec4 a_Position;\n'+
                    'uniform mat4 u_Translation;\n'+
                    'void main(){\n'+
                        'gl_Position = u_Translation * a_Position;\n'+
                    '}\n';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //在x,y,z方向上平移的距離
                var Tx = 0.5, Ty = 0.5, Tz = 0.5;
                var translation = new Float32Array([
                        1.0, 0.0, 0.0, 0.0,
                        0.0, 1.0, 0.0, 0.0,
                        0.0, 0.0, 1.0, 0.0,
                        Tx, Ty, Tz, 1.0
                    ]);

                var u_Translation = gl.getUniformLocation(program, 'u_Translation');
                gl.uniformMatrix4fv(u_Translation, false, translation);
                
                var n = initVertexBuffers(gl);
                if(n < 0){
                    console.log('Failed to set positions of vertices');
                    return;
                }

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

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
image.png

三角形旋轉(zhuǎn)

image.png
image.png
image.png
1、公式代碼實現(xiàn)：
<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            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';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //繞z軸旋轉(zhuǎn)
                var ANGLE = 45.0;
                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);
                
                var n = initVertexBuffers(gl);
                if(n < 0){
                    console.log('Failed to set positions of vertices');
                    return;
                }

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

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
image.png
image.png
2、變換矩陣代碼實現(xiàn)：
<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            var VSHADER_SOURCE = 
                    'attribute vec4 a_Position;\n'+
                    'uniform mat4 u_xformMatrix;\n'+
                    'void main(){\n'+
                        'gl_Position = u_xformMatrix * a_Position;\n'+
                    '}\n';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //繞z軸旋轉(zhuǎn)
                var ANGLE = 45.0;
                var radian = Math.PI * ANGLE / 180.0;
                var cosB = Math.cos(radian);
                var sinB = Math.sin(radian);
                var xformMatrix = new Float32Array([
                        cosB,  sinB, 0.0, 0.0,
                        -sinB, cosB, 0.0, 0.0,
                        0.0,    0.0, 1.0, 0.0,
                        0.0,    0.0, 0.0, 1.0
                    ]);


                var u_xformMatrix = gl.getUniformLocation(program, 'u_xformMatrix');
                gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);;
                
                var n = initVertexBuffers(gl);
                if(n < 0){
                    console.log('Failed to set positions of vertices');
                    return;
                }

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

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
image.png

三角形縮放

image.png
1、公式實現(xiàn)
<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            var VSHADER_SOURCE = 
                    'attribute vec4 a_Position;\n'+
                    'uniform float u_Sx, u_Sy, u_Sz;\n'+
                    'void main(){\n'+
                        'gl_Position.x = u_Sx * a_Position.x;\n'+
                        'gl_Position.y = u_Sy * a_Position.y;\n'+
                        'gl_Position.z = u_Sz * a_Position.z;\n'+
                        'gl_Position.w = 1.0;\n'+
                    '}\n';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //在x,y,z方向上縮放的比例
                var Sx=1.0, Sy=1.5, Sz=1.0;
                var u_Sx = gl.getUniformLocation(program, 'u_Sx');
                var u_Sy = gl.getUniformLocation(program, 'u_Sy');
                var u_Sz = gl.getUniformLocation(program, 'u_Sz');
                gl.uniform1f(u_Sx,Sx);
                gl.uniform1f(u_Sy,Sy);
                gl.uniform1f(u_Sz,Sz);
                
                var n = initVertexBuffers(gl);
                if(n < 0){
                    console.log('Failed to set positions of vertices');
                    return;
                }

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

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
2、矩陣實現(xiàn)
<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            var VSHADER_SOURCE = 
                    'attribute vec4 a_Position;\n'+
                    'uniform mat4 u_Translation;\n'+
                    'void main(){\n'+
                        'gl_Position = u_Translation * a_Position;\n'+
                    '}\n';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //在x,y,z方向上縮放的比例
                var Sx=1.0, Sy=1.5, Sz=1.0;
                var translation = 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_Translation = gl.getUniformLocation(program, 'u_Translation');
                gl.uniformMatrix4fv(u_Translation, false, translation);
                
                var n = initVertexBuffers(gl);
                if(n < 0){
                    console.log('Failed to set positions of vertices');
                    return;
                }

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

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
image.png

示例：旋轉(zhuǎn)的三角形動畫

<!DOCTYPE HTML>
<head>
    
</head>
<html>
    <body onload="main()">
        <canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
            
        </canvas>

        <script type="text/javascript">
            //頂點著色器程序
            var VSHADER_SOURCE = 
                    'attribute vec4 a_Position;\n'+
                    'uniform mat4 u_xformMatrix;\n'+
                    'void main(){\n'+
                        'gl_Position = u_xformMatrix * a_Position;\n'+
                    '}\n';

            //片元著色器程序
            var FSHADER_SOURCE =
                    'void main(){'+
                        'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n'+
                    '}\n';

            function main(){
                //獲取<canvas>元素
                var canvas = document.getElementById("webgl");
                if(!canvas){
                    console.log('error');
                    return;
                }

                //獲取繪制三維圖形的繪圖上下文
                var gl = canvas.getContext('webgl');

                // 創(chuàng)建著色器對象
                const fShader = gl.createShader(gl.FRAGMENT_SHADER);
                const vShader = gl.createShader(gl.VERTEX_SHADER);

                // 將著色器源碼寫入對象
                gl.shaderSource(vShader, VSHADER_SOURCE);
                gl.shaderSource(fShader, FSHADER_SOURCE);

                // 編譯著色器
                gl.compileShader(vShader);
                gl.compileShader(fShader);

                // 創(chuàng)建程序
                const program = gl.createProgram();

                // 程序綁定著色器
                gl.attachShader(program, vShader);
                gl.attachShader(program, fShader);

                // 鏈接程序
                gl.linkProgram(program);

                // 使用程序
                gl.useProgram(program);

                //繞z軸旋轉(zhuǎn)
                var init_angle = 0.0;
                var angle_step = 0.1;
                var current_angle = init_angle;
                setInterval(function(){ 
                    gl.clear(gl.COLOR_BUFFER_BIT);
                    var radian = Math.PI * (current_angle % 360) / 180.0;
                    var cosB = Math.cos(radian);
                    var sinB = Math.sin(radian);
                    var xformMatrix = new Float32Array([
                            cosB,  sinB, 0.0, 0.0,
                            -sinB, cosB, 0.0, 0.0,
                            0.0,    0.0, 1.0, 0.0,
                            0.0,    0.0, 0.0, 1.0
                        ]);


                    var u_xformMatrix = gl.getUniformLocation(program, 'u_xformMatrix');
                    gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);;
                    
                    var n = initVertexBuffers(gl);
                    if(n < 0){
                        console.log('Failed to set positions of vertices');
                        return;
                    }

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

                    current_angle = current_angle + angle_step;
                }, 10);
                

                function initVertexBuffers(gl){
                    var vertices = new Float32Array([0.0, 0.3, -0.1, -0.1, 0.7, -0.7]);     //坐標點位置
                    var n = 3;  //坐標點個數(shù)

                    //創(chuàng)建緩沖區(qū)對象
                    var vertexBuffer = gl.createBuffer();
                    if(!vertexBuffer){
                        console.log('Failed to create the buffer object');
                        return -1;
                    }

                    //將緩沖區(qū)對象綁定到目標
                    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

                    //向緩沖區(qū)對象中寫入數(shù)據(jù)
                    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

                    var a_Position = gl.getAttribLocation(program, 'a_Position');
                    if(a_Position < 0){
                        console.log('Failed to get the storage location of a_Position');
                        return;
                    }

                    //將緩沖區(qū)對象分配給a_Position變量
                    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

                    //連接a_Position變量與分配給它的緩沖區(qū)對象
                    gl.enableVertexAttribArray(a_Position);

                    return n;
                }
            }
        </script>
    </body>
</html>
不同時刻的動畫截圖
image.png
image.png
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