drawing a sphere always at the same size

OpenGL Development JOGL Development
#1

i want to draw a glu sphere(for arcball mouse control), always at the same size, no matter what the distance it is from the camera, or its location relative to the camera

i was thinking to get the 2d postion of the sphere on the viewport(using gluUnproject) then pass this values to
a glOrtho cam:

gl.glMatrixMode(GL.GL_PROJECTION);
gl.glLoadIdentity();

	gl.glOrtho(cam.getFrustLeft(), 
			cam.getFrustRight(), 
			cam.getFrustBottom(), 
			cam.getFrustTop(),
			1, 1000);
	
	
		
	
	gl.glMatrixMode(GL.GL_MODELVIEW);
	gl.glLoadIdentity();

and draw it at the location that is interpolated between the viewport dimensions and the the camera frustum parameters

but i really have the idea it can be easier

any help

Paul

#2

It isn’t clear to me why you need to do the gluUnproject stage to figure out how big the arcball needs to be, or why it needs to be constant size; but the basic idea of using an orthographic projection to get better control of the size of the drawn arcball sounds reasonable.

#3

i’ve almost figured it out, but what i want to do is not to keep my arcball centered at the middle of te screen but it should move along with the center of the object trying to rotate, and thus there rotate around it’s axis, while maintaining a constants 2d size

cheers

Paul

p.s. above code was the first incarnation, right now i’m using viewport coordinates