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glPrimitiveRestartIndex doesn't work as it should in Xcode



  • Hi,

    I have trouble porting my Qt code from Visual Studio to Xcode. I use glPrimitiveRestartIndex to draw many triangle strips with one draw call, and it works nice in Visual Studio, but doesn't work in Xcode. I wrote little function:

    void drawStrip(QOpenGLShaderProgram* program) {
    vector<QVector3D> vertices;
    vertices.push_back(QVector3D(0,1,0));
    vertices.push_back(QVector3D(0,0,0));
    vertices.push_back(QVector3D(1,1,0));
    vertices.push_back(QVector3D(1,0,0));
    vertices.push_back(QVector3D(0,-1,0));
    vertices.push_back(QVector3D(1,-1,0));

    size_t numVertices = 6;
    size_t numTriangles = 2;
    
    GLushort indices[] = {0,1,2,3, 0xFFFF, 1,4,3,5};
    
    
    size_t numIndices = 8;
    
    arrayBuf.bind();
    arrayBuf.allocate(&vertices[0], numVertices*sizeof(QVector3D));
    
    indexBuf.bind();
    indexBuf.allocate(indices, numIndices*sizeof(GLushort));
    
    quintptr offset = 0;
    
    int vertexLocation = program->attributeLocation("a_position");
    program->enableAttributeArray(vertexLocation);
    program->setAttributeBuffer(vertexLocation, GL_FLOAT, offset, 3, sizeof(QVector3D));
    
    glEnable(GL_PRIMITIVE_RESTART);
    glPrimitiveRestartIndex(0xFFFF);
    
    glDrawElements(GL_TRIANGLE_STRIP, numIndices, GL_UNSIGNED_SHORT, 0);
    

    }

    Which should draw two quads one on top of another. It works in VS, as I said, but in Xcode it gives strange result, like it's not restarting indices correctly , 4th triangle is not even drawn and 3th and 4th triangles are flipped.

    Maybe, it's a version of OpenGL that cause troubles - in windows is 4.3, and on Mac is 4.1. I tried including QtOpenGLFunctions_4_1_core.h in Xcode, but that won't even compile - it's gives few BAD ACCESS errors. When I include just QtOpenGLFunctions.h, the result is what I described above.

    What can be problem here? Why does QtOpenGLFunctions_4_1_core gives that errors in Xcode?



  • Ok, I found that glEnable doesn't even enabled GL_PRIMITIVE_RESTART .



  • Ok, actually I found out that glEnable doesn't work (not just for GL_PRIMITIVE_RESTART, but for all enums). I tried to use glEnable directly in GLWidget class, but it doesn't work. What can be problem?


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