can someone help me out with a problem i can’t seem to solve ? given a viewing projection and a modelview matrix is there some way to obtain a pixel to world ratio ? what i need this is to draw 3D objects which are always constant pixel in size even though the orientation is variable. so say i wanted to draw a line that was always 20 pixels in length and initially in the X direction then i would want to do something like :
glBegin(GL_LINES);
glVertex3d(0.,0.,0.);
glVertex3d(20*worldToPixel(),0.,0.);
glEnd();
thanks