Question

我很抱歉粘贴一个代码列表，但它非常简单。我不知道为什么，没有警告没有错误，它在沉默中崩溃。这里是源代码，它引用了一个utils.js文件，我保证外部文件中没有错误。因为其他程序很好地基于这项工作。

<!DOCTYPE html>
<html>
    <head>
        <title>Test</title>
        <style>
            body { background: pink }
            canvas { background: orange }
        </style>
        <script src="utils.js"></script>
        <script id="shader-vs" type="x-shader/x-vertex">
            attribute vec4 aVertexPosition;
            uniform float uCosB, uSinB;

            void main() {
                gl_Position.x = aVertexPosition.x * uCosB - aVertexPosition.y * uSinB;
                gl_Position.y = aVertexPosition.x * uCosB + aVertexPosition.y * uSinB;
                gl_Position.z = aVertexPosition.z;
                gl_Position.w = 1.0;
            }
        </script>
        <script id="shader-fs" type="x-shader/x-fragment">
            void main() {
                gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
            }
        </script>
        <script>
            var gl, canvas, shaderProgram;
            window.onload = function() {
                initCanvasAndGL("canvas");
                initProgram();
                initBuffer();

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

                var angle = 90 / 180 * Math.PI;
                var uSinB = gl.getUniformLocation(shaderProgram, "uSinB");
                var uCosB = gl.getUniformLocation(shaderProgram, "uCosB");
                gl.uniform1f(uSinB, Math.sin(angle));
                gl.uniform1f(uCosB, Math.cos(angle));
                gl.drawArrays(gl.TRIANGLES, 0, 3);
            }

            function initBuffer() {
                var vertices = [0.0, 0.5, -0.5, -0.5, 0.5, -0.5];
                var vertexBuffer = gl.createBuffer();
                gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
                gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);

                var aVertexPosition = gl.getAttribLocation(shaderProgram, "aVertexPosition");
                gl.vertexAttribPointer(aVertexPosition, 2, gl.FLOAT, false, 0, 0);
                gl.enableVertexAttribArray(aVertexPosition);
            }
        </script>
    </head>
    <body>
        <canvas id="canvas" width="400" height="400">
            Canvas Not Supported! :(
        </canvas>
    </body>

If you do suspect the utils.js, Here is the source code.
function initCanvasAndGL(canvasID) {
    canvas = document.getElementById(canvasID);
    var names = [
        "webgl", "experimental-webgl",
        "webkit-3d", "moz-webgl"
    ];

    for(var i = 0; i < names.length; ++i) {
        try {
            gl = canvas.getContext(names[i]);
        } catch(e) {}

        if(gl) {
            break;
        }
    }

    if(!gl) {
        alert("WebGL is not available! :(");
    }
}

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-vertex") {
        shader = gl.createShader(gl.VERTEX_SHADER);
    } else if(shaderScript.type == "x-shader/x-fragment") {
        shader = gl.createShader(gl.FRAGMENT_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;
}

function initProgram() {
    var vertexShader = getShader(gl, "shader-vs");
    var fragmentShader = getShader(gl, "shader-fs");

    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);
}

您可以将它放在一起运行该程序。但结果确实让我发疯了。

Answer 1

是的，正如另一个人评论的那样 - 你需要将你的gl_Position.y更改为

gl_Position.y = aVertexPosition.x * uSinB + aVertexPosition.y * uCosB;

然后你会看到一个红色三角形享受

简单的WebGL程序，RotateTriangle（WebGL编程指南，第3章），无法工作

1 个答案: