Question

我正在尝试使用WebGL显示点（实际上是一个pointcloud）。在过去的2天里，我花了很多时间浏览this教程，并且仍然有很多基于它的代码。

我正在尝试加载.ply文件，然后将每个坐标显示为彩色点，但在尝试绘制时遇到此错误：

[.WebGLRenderingContext-0x111ff17bc300]GL ERROR :GL_INVALID_OPERATION : glDrawArrays: attempt to access out of range vertices in attribute 1

我当然做了一些研究，但一般的答案是缓冲阵列的长度会有所不同，我已经确定不是这样。尽管如此，这很可能是一个类似的noobish错误：

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 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 pointcloudVertexPositionBuffer;
    var pointcloudColourBuffer;
    var pointcloudIndexBuffer;
    function handlePoints(pointCoords, pointColours, indices) {
        pointcloudVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, pointcloudVertexPositionBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(pointCoords), gl.STATIC_DRAW);
        pointcloudVertexPositionBuffer.itemSize = 3;
        pointcloudVertexPositionBuffer.numItems = pointCoords.length / 3;

        pointcloudColourBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, pointcloudColourBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(pointColours), gl.STATIC_DRAW);
        pointcloudColourBuffer.itemSize = 3;
        pointcloudColourBuffer.numItems = pointColours.length / 3;

        pointcloudIndexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, pointcloudIndexBuffer);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW);
        pointcloudIndexBuffer.itemSize = 1;
        pointcloudIndexBuffer.numItems = indices.length;
    }

    var coordList = [];
    var colList = [];
    var indexList = [];
    function loadPLY(){
        jQuery.get('some_ascii.ply', function(data) {
            var lines = data.split('\n');
            var coords = false;

            for(var line = 0; line < lines.length; line++){
                if (coords) {
                    var splitString = lines[line].split(" ");
                    coordList.push(parseFloat(splitString[0]), parseFloat(splitString[1]), parseFloat(splitString[2]));
                    colList.push(parseFloat(splitString[3]), parseFloat(splitString[4]), parseFloat(splitString[5]));
                    indexList.push(parseFloat(line));
                }
                else{
                    if (lines[line] == "end_header"){
                        console.log("end header");
                        coords = true;
                    }
                }
            }
            handlePoints(coordList, colList, indexList);
        });
    }

    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, [0, 0, -6]);

        //gl.uniform1i(shaderProgram.samplerUniform, 0);

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

        gl.bindBuffer(gl.ARRAY_BUFFER, pointcloudVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, pointcloudVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

        setMatrixUniforms();
        //gl.drawElements(gl.TRIANGLES, pointcloudIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
        //console.log("1", pointcloudIndexBuffer.numItems);
        //console.log("2", pointcloudColourBuffer.numItems);
        //console.log("3", pointcloudVertexPositionBuffer.numItems);
        gl.drawArrays(gl.POINTS, 0, pointcloudIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
    }


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

    function webGLStart(){
        var canvas = document.getElementById("canvas");
        initGL(canvas);
        initShaders();
        loadPLY();

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

        tick();
    }

Answer 1

我再次查看了你的代码，我注意到了几件事：

如果要绘制gl.POINT，则需要在顶点着色器中包含table.getColumnModel().getColumn(???).setCellEditor(???);，否则不会绘制点。

您的颜色数据不正确。负面颜色没有意义。

您的drawArrays调用不正确，应为"" QGIS version: 2.11.0 Master (21100) Could not find GRASS 6 Could not find GRASS 7 GEOS_INCLUDE_DIR=GEOS_INCLUDE_DIR-NOTFOUND GEOS_LIBRARY=GEOS_LIBRARY-NOTFOUND CMake Error at cmake/FindGEOS.cmake:182 (MESSAGE): Could not find GEOS Call Stack (most recent call first): CMakeLists.txt:193 (FIND_PACKAGE) Configuring incomplete, errors occurred! See also "C:/QGIS/build/QGIS/CMakeFiles/CMakeOutput.log". See also "C:/QGIS/build/QGIS/CMakeFiles/CMakeError.log". ""

我禁用了透视图，因为如果没有相机知道是否正确绘制了这些东西，但很难看清楚。

您提到的gl_PointSize = 8.0;是因为它在您的.ply数据被解析之前尝试绘制场景。要修复，只在解析完成后才开始绘图。

所以这是我编辑的版本，至少绘制（你必须改变src）：

gl.drawArrays(gl.POINTS, 0, pointcloudIndexBuffer.numItems);

WebGL：绘图点失败：glDrawArrays：“尝试访问属性1中的范围顶点”

1 个答案: