console 命令行工具 X clear

console

window.onload = function() {
    main()
}

var VSHADER_SOURCE = 'attribute vec4 a_Position;\n' + 'attribute vec4 a_Color;\n' + 'uniform mat4 u_ViewMatrix;\n' + 'varying vec4 v_Color;\n' + 'void main() {\n' + '	gl_Position = u_ViewMatrix * a_Position;\n' + '	v_Color = a_Color;\n' + '}\n'

var FSHADER_SOURCE = '#ifdef GL_ES\n' + 'precision mediump float;\n' + '#endif\n' + 'varying vec4 v_Color;\n' + 'void main() {\n' + '  gl_FragColor = v_Color;\n' + '}\n';
function main() {
    var canvas = document.getElementById('webgl');

    var gl = getWebGLContext(canvas);
    if (!gl) {
        console.log('Failed to get the rendering context for WebGL');
        return;
    }

    // Initialize shaders
    if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
        console.log('Failed to intialize shaders.');
        return;
    }
    var n = initVertexBuffers(gl);
    if (n < 0) {
        console.log('Failed to set the vertex information');
        return;
    }
    // Specify the color for clearing <canvas>
    gl.clearColor(0, 0, 0, 1);

    // Get the storage location of u_ViewMatrix
    var u_ViewMatrix = gl.getUniformLocation(gl.program, 'u_ViewMatrix');
    if (!u_ViewMatrix) {
        console.log('Failed to get the storage locations of u_ViewMatrix');
        return;
    }

    // Set the matrix to be used for to set the camera view
    var viewMatrix = new Matrix4();
    viewMatrix.setLookAt(0.20, 0.25, 0.25, 0, 0, 0, 0, 1, 0);

    // Set the view matrix
    gl.uniformMatrix4fv(u_ViewMatrix, false, viewMatrix.elements);

    // Clear <canvas>
    gl.clear(gl.COLOR_BUFFER_BIT);

    // Draw the rectangle
    gl.drawArrays(gl.TRIANGLES, 0, n);
}
function initVertexBuffers(gl) {
    var verticesColors = new Float32Array([
    // Vertex coordinates and color(RGBA)
    0.0, 0.5, -0.4, 0.4, 1.0, 0.4, // The back green one
    - 0.5, -0.5, -0.4, 0.4, 1.0, 0.4, 0.5, -0.5, -0.4, 1.0, 0.4, 0.4,

    0.5, 0.4, -0.2, 1.0, 0.4, 0.4, // The middle yellow one
    - 0.5, 0.4, -0.2, 1.0, 1.0, 0.4, 0.0, -0.6, -0.2, 1.0, 1.0, 0.4,

    0.0, 0.5, 0.0, 0.4, 0.4, 1.0, // The front blue one 
    - 0.5, -0.5, 0.0, 0.4, 0.4, 1.0, 0.5, -0.5, 0.0, 1.0, 0.4, 0.4, ]);
    var n = 9;

    // Create a buffer object
    var vertexColorbuffer = gl.createBuffer();
    if (!vertexColorbuffer) {
        console.log('Failed to create the buffer object');
        return - 1;
    }

    // Write the vertex coordinates and color to the buffer object
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexColorbuffer);
    gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW);

    var FSIZE = verticesColors.BYTES_PER_ELEMENT;
    // Assign the buffer object to a_Position and enable the assignment
    var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
    if (a_Position < 0) {
        console.log('Failed to get the storage location of a_Position');
        return - 1;
    }
    gl.vertexAttribPointer(a_Position, 3, gl.FLOAT, false, FSIZE * 6, 0);
    gl.enableVertexAttribArray(a_Position);

    // Assign the buffer object to a_Color and enable the assignment
    var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
    if (a_Color < 0) {
        console.log('Failed to get the storage location of a_Color');
        return - 1;
    }
    gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 6, FSIZE * 3);
    gl.enableVertexAttribArray(a_Color);

    // Unbind the buffer object
    gl.bindBuffer(gl.ARRAY_BUFFER, null);

    return n;
}

<body>
    <canvas id="webgl" width="400" height="400">
        Please use a browser that supports "canvas"
    </canvas>
</body>

本项目引用的自定义外部资源