Javascript WebGL中的多个程序不起作用

我试图在webgl中使用多个着色器程序，但仍然会遇到问题

看起来，如果我在程序中有不同数量的顶点着色器属性，那么我不会得到没有错误的渲染。是否有一些约束意味着程序必须具有相同数量的属性？更改程序时是否需要禁用/启用属性位置

似乎只是创建多个程序会导致问题，我甚至不必使用第二个着色器，只是创建了它才导致了问题

要创建属性，当所有程序中的属性数相同时，我使用以下代码段可以正常工作：

for ( var i=0 ; i<vertexAttributes.length ; i++ )
{
   shaderProgram[vertexAttributes[i].name] = gl.getAttribLocation(shaderProgram,vertexAttributes[i].name);
   gl.enableVertexAttribArray(shaderProgram[vertexAttributes[i].name]);
}

很抱歉发布了这么多代码，但这最好地说明了这个问题。这是learningwebgl.com教程之一的代码，我所做的只是添加了第二对着色器shader2 fs和shader2 vs以及名为initShaders2的新函数。如果在webGLStart中调用initShaders2与在代码中一样，则不会绘制任何内容？？？我很困惑

<script type="text/javascript" src="two_files/glMatrix-0.js"></script>
<script type="text/javascript" src="two_files/webgl-utils.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 id="shader2-fs" type="x-shader/x-fragment">
    precision mediump float;

    varying vec2 vTextureCoord;
    varying vec3 vLightWeighting;

    uniform sampler2D uSampler;

    void main(void) {
        vec4 textureColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
        gl_FragColor = vec4(textureColor.rgb * vLightWeighting, textureColor.a);
    }
</script>

<script id="shader2-vs" type="x-shader/x-vertex">
    attribute vec3 aVertexPosition;
    attribute vec3 aVertexNormal;
    attribute vec2 aTextureCoord;

    uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;
    uniform mat3 uNMatrix;

    uniform vec3 uAmbientColor;

    uniform vec3 uLightingDirection;
    uniform vec3 uDirectionalColor;

    uniform bool uUseLighting;

    varying vec2 vTextureCoord;
    varying vec3 vLightWeighting;

    void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vTextureCoord = aTextureCoord;

        if (!uUseLighting) {
            vLightWeighting = vec3(1.0, 1.0, 1.0);
        } else {
            vec3 transformedNormal = uNMatrix * aVertexNormal;
            float directionalLightWeighting = max(dot(transformedNormal, uLightingDirection), 0.0);
            vLightWeighting = uAmbientColor + uDirectionalColor * directionalLightWeighting;
        }
    }
</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 shaderProgram2;

    function initShaders2() {
        var fragmentShader = getShader(gl, "shader2-fs");
        var vertexShader = getShader(gl, "shader2-vs");

        shaderProgram2 = gl.createProgram();
        gl.attachShader(shaderProgram2, vertexShader);
        gl.attachShader(shaderProgram2, fragmentShader);
        gl.linkProgram(shaderProgram2);

        if (!gl.getProgramParameter(shaderProgram2, gl.LINK_STATUS)) {
            alert("Could not initialise shaders");
        }

        gl.useProgram(shaderProgram2);

        shaderProgram2.vertexPositionAttribute = gl.getAttribLocation(shaderProgram2, "aVertexPosition");
        gl.enableVertexAttribArray(shaderProgram2.vertexPositionAttribute);

        shaderProgram2.vertexNormalAttribute = gl.getAttribLocation(shaderProgram2, "aVertexNormal");
        gl.enableVertexAttribArray(shaderProgram2.vertexNormalAttribute);

        shaderProgram2.textureCoordAttribute = gl.getAttribLocation(shaderProgram2, "aTextureCoord");
        gl.enableVertexAttribArray(shaderProgram2.textureCoordAttribute);

        shaderProgram2.pMatrixUniform = gl.getUniformLocation(shaderProgram2, "uPMatrix");
        shaderProgram2.mvMatrixUniform = gl.getUniformLocation(shaderProgram2, "uMVMatrix");
        shaderProgram2.nMatrixUniform = gl.getUniformLocation(shaderProgram2, "uNMatrix");
        shaderProgram2.samplerUniform = gl.getUniformLocation(shaderProgram2, "uSampler");
        shaderProgram2.useLightingUniform = gl.getUniformLocation(shaderProgram2, "uUseLighting");
        shaderProgram2.ambientColorUniform = gl.getUniformLocation(shaderProgram2, "uAmbientColor");
        shaderProgram2.lightingDirectionUniform = gl.getUniformLocation(shaderProgram2, "uLightingDirection");
        shaderProgram2.directionalColorUniform = gl.getUniformLocation(shaderProgram2, "uDirectionalColor");
    }

    var mvMatrix = mat4.create();
    var mvMatrixStack = [];
    var pMatrix = mat4.create();

    function mvPushMatrix() {
        var copy = mat4.create();
        mat4.set(mvMatrix, copy);
        mvMatrixStack.push(copy);
    }

    function mvPopMatrix() {
        if (mvMatrixStack.length == 0) {
            throw "Invalid popMatrix!";
        }
        mvMatrix = mvMatrixStack.pop();
    }


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


    function degToRad(degrees) {
        return degrees * Math.PI / 180;
    }


    var pyramidVertexPositionBuffer;
    var pyramidVertexColorBuffer;
    var cubeVertexPositionBuffer;
    var cubeVertexColorBuffer;
    var cubeVertexIndexBuffer;

    function initBuffers() {
        pyramidVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
        var vertices = [
            // Front face
             0.0,  1.0,  0.0,
            -1.0, -1.0,  1.0,
             1.0, -1.0,  1.0,

            // Right face
             0.0,  1.0,  0.0,
             1.0, -1.0,  1.0,
             1.0, -1.0, -1.0,

            // Back face
             0.0,  1.0,  0.0,
             1.0, -1.0, -1.0,
            -1.0, -1.0, -1.0,

            // Left face
             0.0,  1.0,  0.0,
            -1.0, -1.0, -1.0,
            -1.0, -1.0,  1.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        pyramidVertexPositionBuffer.itemSize = 3;
        pyramidVertexPositionBuffer.numItems = 12;

        pyramidVertexColorBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
        var colors = [
            // Front face
            1.0, 0.0, 0.0, 1.0,
            0.0, 1.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,

            // Right face
            1.0, 0.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
            0.0, 1.0, 0.0, 1.0,

            // Back face
            1.0, 0.0, 0.0, 1.0,
            0.0, 1.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,

            // Left face
            1.0, 0.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
            0.0, 1.0, 0.0, 1.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
        pyramidVertexColorBuffer.itemSize = 4;
        pyramidVertexColorBuffer.numItems = 12;


        cubeVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
        vertices = [
            // Front face
            -1.0, -1.0,  1.0,
             1.0, -1.0,  1.0,
             1.0,  1.0,  1.0,
            -1.0,  1.0,  1.0,

            // Back face
            -1.0, -1.0, -1.0,
            -1.0,  1.0, -1.0,
             1.0,  1.0, -1.0,
             1.0, -1.0, -1.0,

            // Top face
            -1.0,  1.0, -1.0,
            -1.0,  1.0,  1.0,
             1.0,  1.0,  1.0,
             1.0,  1.0, -1.0,

            // Bottom face
            -1.0, -1.0, -1.0,
             1.0, -1.0, -1.0,
             1.0, -1.0,  1.0,
            -1.0, -1.0,  1.0,

            // Right face
             1.0, -1.0, -1.0,
             1.0,  1.0, -1.0,
             1.0,  1.0,  1.0,
             1.0, -1.0,  1.0,

            // Left face
            -1.0, -1.0, -1.0,
            -1.0, -1.0,  1.0,
            -1.0,  1.0,  1.0,
            -1.0,  1.0, -1.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        cubeVertexPositionBuffer.itemSize = 3;
        cubeVertexPositionBuffer.numItems = 24;

        cubeVertexColorBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
        colors = [
            [1.0, 0.0, 0.0, 1.0], // Front face
            [1.0, 1.0, 0.0, 1.0], // Back face
            [0.0, 1.0, 0.0, 1.0], // Top face
            [1.0, 0.5, 0.5, 1.0], // Bottom face
            [1.0, 0.0, 1.0, 1.0], // Right face
            [0.0, 0.0, 1.0, 1.0]  // Left face
        ];
        var unpackedColors = [];
        for (var i in colors) {
            var color = colors[i];
            for (var j=0; j < 4; j++) {
                unpackedColors = unpackedColors.concat(color);
            }
        }
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(unpackedColors), gl.STATIC_DRAW);
        cubeVertexColorBuffer.itemSize = 4;
        cubeVertexColorBuffer.numItems = 24;

        cubeVertexIndexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
        var cubeVertexIndices = [
            0, 1, 2,      0, 2, 3,    // Front face
            4, 5, 6,      4, 6, 7,    // Back face
            8, 9, 10,     8, 10, 11,  // Top face
            12, 13, 14,   12, 14, 15, // Bottom face
            16, 17, 18,   16, 18, 19, // Right face
            20, 21, 22,   20, 22, 23  // Left face
        ];
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
        cubeVertexIndexBuffer.itemSize = 1;
        cubeVertexIndexBuffer.numItems = 36;
    }


    var rPyramid = 0;
    var rCube = 0;

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

        mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

        mat4.identity(mvMatrix);

        mat4.translate(mvMatrix, [-1.5, 0.0, -8.0]);

        mvPushMatrix();
        mat4.rotate(mvMatrix, degToRad(rPyramid), [0, 1, 0]);

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

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

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

        mvPopMatrix();


        mat4.translate(mvMatrix, [3.0, 0.0, 0.0]);

        mvPushMatrix();
        mat4.rotate(mvMatrix, degToRad(rCube), [1, 1, 1]);

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

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

        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
        setMatrixUniforms();
        gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);

        mvPopMatrix();

    }


    var lastTime = 0;

    function animate() {
        var timeNow = new Date().getTime();
        if (lastTime != 0) {
            var elapsed = timeNow - lastTime;

            rPyramid += (90 * elapsed) / 1000.0;
            rCube -= (75 * elapsed) / 1000.0;
        }
        lastTime = timeNow;
    }


    function tick() {
        requestAnimFrame(tick);
        drawScene();
        animate();
    }


    function webGLStart() {
        var canvas = document.getElementById("lesson04-canvas");
        initGL(canvas);
        initShaders2();  // !!!!!!!!!!!!!!!!!!!!!!!!!
        initShaders();
        initBuffers();

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

        tick();
    }

</script>


</head>


<body onload="webGLStart();">
    <a href="http://learningwebgl.com/blog/?p=370">&lt;&lt; Back to Lesson 4</a><br>

    <canvas id="lesson04-canvas" style="border: none;" width="500" height="500"></canvas>

    <br>
    <a href="http://learningwebgl.com/blog/?p=370">&lt;&lt; Back to Lesson 4</a><br>

</body></html>

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您可能需要给我们提供更多的信息，但为了让您开始，这里有一个快速清单。无论何时更改程序，您都希望：

启用相应的顶点属性数组 绑定顶点属性指针，即使它们已绑定到正确的缓冲区 绑定任何需要的制服，如纹理采样器。

---

基本上，您希望在每次更改程序时都将其视为第一次设置抽签呼叫。

您可能需要向我们提供更多信息，但为了让您开始，这里有一个快速清单。无论何时更改程序，您都希望：

启用相应的顶点属性数组 绑定顶点属性指针，即使它们已绑定到正确的缓冲区 绑定任何需要的制服，如纹理采样器。

---

基本上，您希望在每次更改程序时都将其视为第一次设置抽签呼叫。

感谢您的帮助！我没有给你足够的信息来解决这个问题，但是你给我的信息让我想到了正确的方法。干杯谢谢你的洞察力！我没有给你足够的信息来解决这个问题，但是你给我的信息让我想到了正确的方法。干杯