This example shows how to position a GL_LIGHT on the camera.
A spot light position and direction are set so that they always match the camera's current setup.
This is done using the camera->position()
and camera->viewDirection()
methods which return values expressed in the world coordinates system.
#include <QGLViewer/qglviewer.h> class Viewer : public QGLViewer { protected : virtual void draw(); virtual void init(); virtual QString helpString() const; private : virtual void drawSpiral(); };
#include "cameraLight.h" using namespace std; using namespace qglviewer; void Viewer::draw() { // Place light at camera position const Vec cameraPos = camera()->position(); const GLfloat pos[4] = {cameraPos[0], cameraPos[1], cameraPos[2], 1.0}; glLightfv(GL_LIGHT1, GL_POSITION, pos); // Orientate light along view direction glLightfv(GL_LIGHT1, GL_SPOT_DIRECTION, camera()->viewDirection()); drawSpiral(); } // Draws a spiral void Viewer::drawSpiral() { const float nbSteps = 1000.0; 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() { // Light setup glDisable(GL_LIGHT0); glEnable(GL_LIGHT1); // Light default parameters const GLfloat light_ambient[4] = {1.0, 1.0, 1.0, 1.0}; const GLfloat light_specular[4] = {1.0, 1.0, 1.0, 1.0}; const GLfloat light_diffuse[4] = {1.0, 1.0, 1.0, 1.0}; glLightf( GL_LIGHT1, GL_SPOT_EXPONENT, 3.0); glLightf( GL_LIGHT1, GL_SPOT_CUTOFF, 10.0); glLightf( GL_LIGHT1, GL_CONSTANT_ATTENUATION, 0.1f); glLightf( GL_LIGHT1, GL_LINEAR_ATTENUATION, 0.3f); glLightf( GL_LIGHT1, GL_QUADRATIC_ATTENUATION, 0.3f); glLightfv(GL_LIGHT1, GL_AMBIENT, light_ambient); glLightfv(GL_LIGHT1, GL_SPECULAR, light_specular); glLightfv(GL_LIGHT1, GL_DIFFUSE, light_diffuse); // Restore previous viewer state. restoreStateFromFile(); // Opens help window help(); } QString Viewer::helpString() const { QString text("<h2>C a m e r a L i g h t</h2>"); text += "See the <b>Mouse</b> tab and the documentation web pages for details.<br><br>"; text += "Press <b>Escape</b> to exit the viewer."; return text; }
#include "cameraLight.h" #include <qapplication.h> int main(int argc, char** argv) { // Read command lines arguments. QApplication application(argc,argv); // Instantiate the viewer. Viewer viewer; viewer.setWindowTitle("cameraLight"); // Make the viewer window visible on screen. viewer.show(); // Run main loop. return application.exec(); }
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