Mixing OpenGL (3D) and QPainter (2D) drawing in the same viewer.
A semi-transparent eounded square is painted in 2D using a QPainter on top of a classical 3D OpenGL rendering. Useful to add 2D objects (annotations, menus, head-up display) to your viewers.
Inspired from the Qt's overpainting example. Note that this functionnality is only available with Qt 4.
#include <QGLViewer/qglviewer.h> class QPaintEvent; class QPainter; class Viewer : public QGLViewer { public : Viewer(QWidget* parent = 0); protected : virtual void draw(); virtual void init(); void drawOverpaint(QPainter *painter); virtual void paintGL() { update(); }; virtual void paintEvent(QPaintEvent *event); // Could be overloaded to defer final initializations //virtual void showEvent(QShowEvent *event); virtual QString helpString() const; };
#include "viewer.h" #include <qapplication.h> int main(int argc, char** argv) { QApplication application(argc,argv); Viewer viewer; viewer.setWindowTitle("overpainting"); viewer.show(); return application.exec(); }
#include "viewer.h" #include <QPainter> using namespace std; #ifndef GL_MULTISAMPLE #define GL_MULTISAMPLE 0x809D #endif Viewer::Viewer(QWidget* parent) : QGLViewer(QGLFormat(QGL::SampleBuffers), parent) { setAttribute(Qt::WA_NoSystemBackground); } void Viewer::drawOverpaint(QPainter *painter) { painter->save(); painter->translate(width()/2, height()/2); QRadialGradient radialGrad(QPointF(-40, -40), 100); radialGrad.setColorAt(0, QColor(255, 255, 255, 100)); radialGrad.setColorAt(1, QColor(200, 200, 0, 100)); painter->setBrush(QBrush(radialGrad)); painter->drawRoundRect(-100, -100, 200, 200); painter->restore(); } // Draws a spiral void Viewer::draw() { const float nbSteps = 200.0; glBegin(GL_QUAD_STRIP); for (int i=0; i<nbSteps; ++i) { const float ratio = i/nbSteps; const float angle = 21.0*ratio; const float c = cos(angle); const float s = sin(angle); const float r1 = 1.0 - 0.8f*ratio; const float r2 = 0.8f - 0.8f*ratio; const float alt = ratio - 0.5f; const float nor = 0.5f; const float up = sqrt(1.0-nor*nor); glColor3f(1.0-ratio, 0.2f , ratio); glNormal3f(nor*c, up, nor*s); glVertex3f(r1*c, alt, r1*s); glVertex3f(r2*c, alt+0.05f, r2*s); } glEnd(); } void Viewer::init() { restoreStateFromFile(); help(); } void Viewer::paintEvent(QPaintEvent *event) { Q_UNUSED(event) QPainter painter; painter.begin(this); painter.setRenderHint(QPainter::Antialiasing); // Save current OpenGL state glPushAttrib(GL_ALL_ATTRIB_BITS); glMatrixMode(GL_PROJECTION); glPushMatrix(); glMatrixMode(GL_MODELVIEW); glPushMatrix(); // Reset OpenGL parameters glShadeModel(GL_SMOOTH); glEnable(GL_DEPTH_TEST); glEnable(GL_CULL_FACE); glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glEnable(GL_MULTISAMPLE); static GLfloat lightPosition[4] = { 1.0, 5.0, 5.0, 1.0 }; glLightfv(GL_LIGHT0, GL_POSITION, lightPosition); qglClearColor(backgroundColor()); // Classical 3D drawing, usually performed by paintGL(). preDraw(); draw(); postDraw(); // Restore OpenGL state glMatrixMode(GL_MODELVIEW); glPopMatrix(); glMatrixMode(GL_PROJECTION); glPopMatrix(); glPopAttrib(); drawOverpaint(&painter); painter.end(); } QString Viewer::helpString() const { QString text("<h2>O v e r p a i n t</h2>"); text += "This example shows how to mix the 2D QPainter drawing with regular 3D in an OpenGL QGLViewer.<br>"; text += "The <code>paintEvent</code> method is overloaded to interleave the two drawing codes."; return text; }
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