All Canvas3D rendering is broken when GL ES 3.0 is requested



  • I've distilled this to a completely trivial testcase. In main() I request a GL ES 3.0 context. In the Canvas3D code I first I setup all low-level stuff like shaders, vertex buffers and matrices. Then I draw a white triangle. The results is a window that alternates between all black and white (flickers) at a high frequency. I.e. completely buggy.

    Changing the 3.0 version I request to 2.0 fixes it, and, in my real app, and lets all other GL functionality work fine.

    Note that QML items other than the Canvas3D are rendered fine.

    Platforms note: This has been tested only on Windows 7 with an Intel GPU.

    My code:

    I based my testcase on the textureandlight sample app bundled with Qt. Since mine is a derived work, I have to first post the license terms here:

    /****************************************************************************
    **
    ** Copyright (C) 2016 The Qt Company Ltd.
    ** Contact: https://www.qt.io/licensing/
    **
    ** This file is part of the QtCanvas3D module of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** Commercial License Usage
    ** Licensees holding valid commercial Qt licenses may use this file in
    ** accordance with the commercial license agreement provided with the
    ** Software or, alternatively, in accordance with the terms contained in
    ** a written agreement between you and The Qt Company. For licensing terms
    ** and conditions see https://www.qt.io/terms-conditions. For further
    ** information use the contact form at https://www.qt.io/contact-us.
    **
    ** BSD License Usage
    ** Alternatively, you may use this file under the terms of the BSD license
    ** as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
    **   * Neither the name of The Qt Company Ltd nor the names of its
    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
    **
    **
    ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/
    

    And now for the actual source.

    main.cpp:

    #include <QGuiApplication>
    #include <QQmlApplicationEngine>
    #include <QSurfaceFormat>
    
    static QSurfaceFormat createSurfaceFormat() {
        QSurfaceFormat format;
        format.setVersion(3, 0);
        return format;
    }
    
    int main(int argc, char *argv[])
    {
        QSurfaceFormat::setDefaultFormat(::createSurfaceFormat());
        QGuiApplication::setAttribute(Qt::AA_UseOpenGLES);
        QGuiApplication app(argc, argv);
        
        QQmlApplicationEngine engine;
        engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
        
        return app.exec();
    }
    

    main.qml:

    import QtQuick 2.0
    import QtCanvas3D 1.0
    import QtQuick.Window 2.0
    
    import "GLCode.js" as GLCode
    
    Window {
        width: 800
        height: 500
        visible: true
        
        Canvas3D {
            anchors.fill: parent
            
            id: canvas3d
            
            onInitializeGL: {
                GLCode.initializeGL();
            }
        
            onPaintGL: {
                GLCode.paintGL();
            }
        
            onResizeGL: {
                GLCode.resizeGL();
            }
        }
    }
    

    GLCode.js:

    Qt.include("gl-matrix.js")
    
    var gl;
    var vertexPositionAttribute;
    var mvMatrix = mat4.create();
    var pMatrix  = mat4.create();
    var pMatrixUniform;
    var mvMatrixUniform;
    var colorUniform; // unused. removing it produced a weird error. please ignore.
    
    function initializeGL() {
        gl = canvas3d.getContext("canvas3d");
    
        gl.disable(gl.DEPTH_TEST);
        gl.disable(gl.CULL_FACE);
        gl.clearColor(0.0, 0.0, 0.0, 1.0);
    
        initShaders();
    
        initBuffers();
    }
    
    function resizeGL()
    {
        gl.viewport(0, 0, canvas3d.width, canvas3d.height);
        mat4.perspective(pMatrix, degToRad(45), canvas3d.width / canvas3d.height, 0.1, 500.0);
        gl.uniformMatrix4fv(pMatrixUniform, false, pMatrix);
    }
    
    function degToRad(degrees) {
        return degrees * Math.PI / 180;
    }
    
    function paintGL() {
        gl.clear(gl.COLOR_BUFFER_BIT);
        
        mat4.identity(mvMatrix);
        mat4.translate(mvMatrix, mvMatrix, [0, 0, -10.0]);
        
        gl.uniformMatrix4fv(mvMatrixUniform, false, mvMatrix);
        gl.drawElements(gl.TRIANGLES, 3, gl.UNSIGNED_SHORT, 0);
    }
    
    function initBuffers()
    {
        var cubeVertexPositionBuffer = gl.createBuffer();
        cubeVertexPositionBuffer.name = "cubeVertexPositionBuffer";
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
        gl.bufferData(gl.ARRAY_BUFFER,
                    new Float32Array([
                                            -1.0, -1.0,
                                            1.0, -1.0,
                                            1.0,  1.0
                                     ]),
                    gl.STATIC_DRAW);
        
        gl.vertexAttribPointer(vertexPositionAttribute, 2, gl.FLOAT, false, 0, 0);
    
        var cubeVertexIndexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,
                      new Uint16Array([0,  1,  2]),
                      gl.STATIC_DRAW);
    }
    
    function initShaders()
    {
        var vertexShader = getShader(gl,
                                      "attribute highp vec3 aVertexPosition;  \
                                                                             \
                                      uniform mat4 uMVMatrix;                \
                                      uniform mat4 uPMatrix;                 \
                                                                             \
                                      void main(void) {                      \
                                          gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0); \
                                      }"
                                     , gl.VERTEX_SHADER);
        var fragmentShader = getShader(gl,
                                       "void main(void) {                  \
                                            gl_FragColor = vec4(1.0);           \
                                        }"
                                       , gl.FRAGMENT_SHADER);
        var shaderProgram = gl.createProgram();
    
        gl.attachShader(shaderProgram, vertexShader);
        gl.attachShader(shaderProgram, fragmentShader);
    
        gl.linkProgram(shaderProgram);
    
        if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
            console.log("Could not initialise shaders");
            console.log(gl.getProgramInfoLog(shaderProgram));
        }
    
        gl.useProgram(shaderProgram);
    
        vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
        gl.enableVertexAttribArray(vertexPositionAttribute);
    
        pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
        mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
    }
    
    function getShader(gl, str, type) {
        var shader = gl.createShader(type);
        gl.shaderSource(shader, str);
        gl.compileShader(shader);
    
        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            console.log("JS:Shader compile failed");
            console.log(gl.getShaderInfoLog(shader));
            return null;
        }
    
        return shader;
    }
    

    Required js libary: "glMatrix 2.2.2". I can't find this exact version from its official site, but you can get almost the same version (2.2.1) here.

    I've also uploaded the complete testcase project here, if you want to run it more easily. (the download button is at the top-right corner of that page). Please ignore the confusing project name, it's a leftover.


  • Lifetime Qt Champion

    Hi,

    I'd recommend checking out the bug report system to see if it's something known. If not then please consider opening a new report providing your sample application as well as system specification.



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