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POFail to generate a triangle by openGL with Qt5.0.2
 

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  1. POFail to generate a triangle by openGL with Qt5.0.2
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    <p>OS : mac osx 10.8.3</p> <hr> <p>compiler : clang3.2</p> <hr> <p>I am a beginner of opengl, trying to play opengl with Qt5</p> <p>There are two problems about this simple program(plot a triangle)</p> <ol> <li><p>I can't see the triangle</p></li> <li><p>The program could not exit even I close the window</p></li> </ol> <p>hpp</p> <pre><code>#include &lt;QGLWidget&gt; #include &lt;QtGui/QOpenGLFunctions&gt; #include &lt;QtGui/QOpenGLShaderProgram&gt; class QWidget; class ch1HelloTriangle : public QGLWidget, protected QOpenGLFunctions { Q_OBJECT public: explicit ch1HelloTriangle(QWidget *parent = 0); protected: virtual void initializeGL(); void initShaders(); void InitializeVertexBuffer(); virtual void resizeGL(int w, int h); virtual void paintGL(); private: QOpenGLShaderProgram program; GLuint positionBufferObject; }; </code></pre> <p>.cpp</p> <pre><code>#include &lt;locale.h&gt; #include &lt;QWidget&gt; #include "ch1HelloTriangle.hpp" namespace { float const vertexPositions[] = { 0.75f, 0.75f, 0.0f, 1.0f, 0.75f, -0.75f, 0.0f, 1.0f, -0.75f, -0.75f, 0.0f, 1.0f, }; } ch1HelloTriangle::ch1HelloTriangle(QWidget *parent) : QGLWidget(parent) { } void ch1HelloTriangle::initializeGL() { initializeOpenGLFunctions(); InitializeVertexBuffer(); initShaders(); } void ch1HelloTriangle::initShaders() { // Override system locale until shaders are compiled setlocale(LC_NUMERIC, "C"); // Compile vertex shader if (!program.addShaderFromSourceCode(QOpenGLShader::Vertex, "attribute vec4 position;\n" "void main()\n" "{\n" " gl_Position = position;\n" "}\n")) { close(); } // Compile fragment shader if (!program.addShaderFromSourceCode(QOpenGLShader::Fragment, "out vec4 outputColor;\n" "void main()\n" "{\n" " outputColor = vec4(1.0f, 1.0f, 1.0f, 1.0f);\n" "}\n")) { close(); } // Link shader pipeline if (!program.link()) close(); // Bind shader pipeline for use if (!program.bind()) close(); // Restore system locale setlocale(LC_ALL, ""); } void ch1HelloTriangle::InitializeVertexBuffer() { glGenBuffers(1, &amp;positionBufferObject); glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject); glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); } void ch1HelloTriangle::resizeGL(int w, int h) { // Set OpenGL viewport to cover whole widget glViewport(0, 0, w, h); } void ch1HelloTriangle::paintGL() { /* //codes propose by http://stackoverflow.com/questions/13111291/displaying-a-triangle-with-qt-and-opengl?rq=1, can't see the triangle either QSize viewport_size = size(); glViewport(0, 0, viewport_size.width(), viewport_size.height()); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glFrustum(-1, 1, -1, 1, 5, 7); // near and far match your triangle Z distance glMatrixMode(GL_MODELVIEW);*/ glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glClear(GL_COLOR_BUFFER_BIT); glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject); int vertexLocation = program.attributeLocation("position"); program.enableAttributeArray(vertexLocation); glVertexAttribPointer(vertexLocation, 4, GL_FLOAT, GL_FALSE, 0, 0); glDrawArrays(GL_TRIANGLES, 0, 3); } </code></pre> <p>main.cpp</p> <pre><code>#include &lt;QApplication&gt; #include "ch1HelloTriangle.hpp" int main(int argc, char *argv[]) { QApplication a(argc, argv); ch1HelloTriangle ch1; ch1.show(); return a.exec(); } </code></pre>
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    1. USStereoMatching
    1. USStereoMatching
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    1. COI see that you had code to set the projection matrix but removed it. Why? If you're using the fixed-function pipeline, that's probably why you aren't seeing the triangle. If you're not using the fixed-function pipeline, then please show your vertex shader, too.
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      1. POFail to generate a triangle by openGL with Qt5.0.2
      1. USuser1118321
    2. COI removed it because the results would be the same even I add those lines.Besides, the vertex shader and fragments shader are inside the function "initShaders".The function read the shaders from the source codes.
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      1. POFail to generate a triangle by openGL with Qt5.0.2
      1. USStereoMatching
    3. COThe answer to your second question lies in the first line of your post. You are on Mac OS, this is the way it works. Closing the window does not close the application, you need to use `Cmd+q` to close the application.
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      1. POFail to generate a triangle by openGL with Qt5.0.2
      1. USAnton Guryanov
 

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