Hello, When I draw my objects (class Triangle) with glRecti() picking with gluPickMatrix() works fine. But when I draw them with glBegin(GL_TRIANGLES)glVertex()...glEnd(), it seems like _all_ the objects that are drawn are selected independently from where I click on the screen (slightly modified example 13-3 red book). Why cant I pick the things drawn with glBegin()... correctly? What does glRecti do that the the other drawing routine does not? Thank you for your time and answers. I am sorry if the example is to long, I could not shorten it more. The following example code compiles and works. It stops working if you enable the other drawing routine. peter #include <gl\glut.h> #include <vector> #include <iostream> class Triangle{ public: Triangle( GLuint name, int pos ):m_name(name),m_pos(pos){} void draw()const{ glLoadName(m_name); glColor3f(1,0,0); glRecti (m_pos, m_pos, m_pos + 10, m_pos + 10); //works /* glBegin(GL_TRIANGLES); //does not work: glVertex3f(9 + m_pos, 10,0); glVertex3f(14 + m_pos,10,0); glVertex3f(11 + m_pos,5,0); glEnd(); //glFlush(); */ } private: GLuint m_name; int m_pos; }; std::vector <triangle> triangles; const int HITBUFSIZE = 512; void process_Hits( GLint hits, GLuint buffer[] ){ std::cerr << "hits: " << hits << "\n"; GLuint *ptr = (GLuint*)buffer; for (GLint i = 0; i < hits; i++) { GLuint names = *ptr; std::cerr << "number of names for this hit = " << names << "\n"; ptr++; std::cerr << "z1: " << (*ptr/0x7fffffff); ptr++; std::cerr << " z2: " << (*ptr/0x7fffffff); ptr++; std::cerr << "\nnames: "; for( GLuint j = 0; j < names; j++){ std::cerr << (*ptr) << " "; ptr++; } std::cerr << "\n"; } std::cerr << "\n\n"; } void drawObjects(){ for( std::vector<triangle>::const_iterator ti = triangles.begin(); ti != triangles.end(); ++ti){ (*ti).draw(); } } void selectObjects(int button, int state, int x, int y){ if (button != GLUT_LEFT_BUTTON || state != GLUT_DOWN){ return; } GLint viewport[4]; glGetIntegerv (GL_VIEWPORT, viewport); GLuint selectBuf[HITBUFSIZE]; glSelectBuffer (HITBUFSIZE, selectBuf); glRenderMode (GL_SELECT); glInitNames(); glPushName(0); glMatrixMode (GL_PROJECTION); glPushMatrix (); glLoadIdentity (); gluPickMatrix ((GLdouble) x, (GLdouble)(viewport[3]-y),5, 5, viewport); glOrtho (-50.0, 50.0, -50.0, 50.0, 20.0, -20.0); glMatrixMode(GL_MODELVIEW); drawObjects(); glMatrixMode (GL_PROJECTION); glPopMatrix (); glFlush (); GLint hits = glRenderMode (GL_RENDER); process_Hits (hits, selectBuf); glutPostRedisplay(); } void display(){ glClear (GL_COLOR_BUFFER_BIT); drawObjects(); glFlush (); } void reshape (int w, int h){ glViewport (0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode (GL_PROJECTION); glLoadIdentity (); glOrtho (-50.0, 50.0, -50.0, 50.0, 20.0, -20.0); glMatrixMode (GL_MODELVIEW); glLoadIdentity (); } void init(void){ glClearColor (0.0, 0.0, 0.0, 0.0); glShadeModel (GL_FLAT); } int main(int argc, char** argv){ glutInit(&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); glutInitWindowSize (500, 500); glutInitWindowPosition (100, 100); glutCreateWindow (argv[0]); triangles.push_back(Triangle(1,10)); triangles.push_back(Triangle(2,20)); triangles.push_back(Triangle(3,30)); triangles.push_back(Triangle(4,40)); init (); glutMouseFunc (selectObjects); glutDisplayFunc(display); glutReshapeFunc(reshape); glutMainLoop(); return 0; }