gluLookAt with cone not showing expected result

Question

I am trying to look at a cone in 3D, for which I used gluLookAt. I draw a cone in the middle of the screen at pos (250, 250, 0) and then look at it with a camera above the origin looking at the middle. The output is a circle, contrary to the cone I expected to see. It seems the camera is instead at point (250,250,0) also, but it is specified in gluLookAt it should be above the origin. What am I overlooking here? void display(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(250, 250, 0); glutSolidCone(30, 10, 20, 20); glTranslatef(-250, -250, 0); gluLookAt(0, 0, 100, 250, 250, 0, 0, 0, 1); glFlush(); glutSwapBuffers(); } int main(int argc, char **argv) { float x, y; glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH); glutInitWindowSize(500, 500); glutCreateWindow("Cone"); glutDisplayFunc(display); glutReshapeFunc(reshape); glutKeyboardFunc(keyboard); glutMotionFunc(drag); glutMouseFunc(click); glutSpecialFunc(catchKey); glEnable(GL_DEPTH_TEST); glutMainLoop(); //calls do_one_simulation_step, keyboard, display, drag, reshape return 0; } JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

A few issues: Set your camera matrix, then draw. The way you have it now your gluLookAt() does nothing useful. The default identity projection matrix probably isn't what you want. Set a real perspective transform using gluPerspective() or glFrustum(). Your gluLookAt() eye/center coords were a bit wonky; I've put the eye at (50, 50, 50) and set it to look at the origin. All together: #include #include void display( void ) { glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); glMatrixMode( GL_PROJECTION ); glLoadIdentity(); double w = glutGet( GLUT_WINDOW_WIDTH ); double h = glutGet( GLUT_WINDOW_HEIGHT ); gluPerspective( 60.0, w / h, 1.0, 1000.0 ); glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); gluLookAt( 50, 50, 50, 0, 0, 0, 0, 0, 1 ); glutWireCone( 10, 30, 20, 20 ); glutSwapBuffers(); } int main( int argc, char **argv ) { glutInit( &argc, argv ); glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH ); glutInitWindowSize( 500, 500 ); glutCreateWindow( "Cone" ); glutDisplayFunc( display ); glEnable( GL_DEPTH_TEST ); glutMainLoop(); return 0; }