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The fastDraw()
function keeps interactivity even with large scenes.
This example demonstrates the use of the fastDraw()
function, which
is called when the camera moves. This function is usefull for displaying very
complex scene, while keeping an interactive camera motion.
#include <QGLViewer/qglviewer.h> class Viewer : public QGLViewer { protected: virtual void init(); virtual void draw(); virtual void fastDraw(); virtual QString helpString() const; };
#include "fastDraw.h" using namespace std; using namespace qglviewer; void Viewer::init() { // Increase the material shininess, so that the difference between // the two versions of the spiral is more visible. glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 50.0); GLfloat specular_color[4] = { 0.8, 0.8, 0.8, 1.0 }; glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, specular_color); restoreFromFile(); help(); } static void drawSpiral(bool simplified = false) { int nbSteps = 600; int nbSub = 50; if (simplified) { nbSteps = 60; nbSub = 2; } for (float n=0; n<nbSub; ++n) { glBegin(GL_QUAD_STRIP); for (float i=0.0; i<nbSteps; ++i) { float ratio = i/nbSteps; float angle = 21.0*ratio; float radius = 1.0 - 0.5*ratio; Vec center(radius*cos(angle), ratio-0.5, radius*sin(angle)); for (unsigned short j=0; j<2; ++j) { float delta = 3.0*(n+j)/nbSub; Vec shift(cos(angle)*cos(delta), sin(delta), sin(angle)*cos(delta)); glColor3f(1-ratio, (n+j)/nbSub , ratio); glNormal3fv(shift.address()); glVertex3fv((center+0.2*shift).address()); } } glEnd(); } } void Viewer::draw() { drawSpiral(); } void Viewer::fastDraw() { drawSpiral(true); } QString Viewer::helpString() const { QString text("<h2>F a s t D r a w</h2>"); text += "The <i>fastDraw()</i> function is called instead of <i>draw()</i> when the camera is manipulated, "; text += "thus allowing interactive displacements even with very complex scenes, as soon as you provide a fast drawing function."; return text; }
#include "fastDraw.h" #include <qapplication.h> int main(int argc, char** argv) { // Read command lines arguments. QApplication application(argc,argv); // Instantiate the viewer. Viewer v; // Make the viewer window visible on screen. v.show(); // Set the viewer as the application main widget. application.setMainWidget(&v); // Run main loop. return application.exec(); }
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