OpenGL, overlapping circles

[LEDZ]

I'm experimenting with a widget that uses DrawWorld to draw circles.
Does anyone know how the following could be done:


Essentially the overlapped parts are removed.
It would be awesome if someone knows how to do this.

[zwzsg]

Use the brute way! Calculate which circles intersect, and where, then draw only the segment that are outside the intersecting slice. Since it only involves circles in a 2D plane, the calculation involved are not that complicated.

[LEDZ]

Thats all very well, but I am a OpenGL noob.
How do I draw only a part circle. So far I have used gl.DrawGroundCircle

[zwzsg]

A bit like that (not tested):

Code: Select all

local function YourVertFunction()
	for angle=0,2*math.pi*3/4,math.pi/32 do
		gl.Vertex(x+r*math.cos(a),y,z+r*math.sin(a))
	end
end

gl.BeginEnd(GL.LINE_LOOP,YourVertFunction)

[aegis]

The UnitShapes widget uses OpenGL tricks to do seamlessly-merged circles/shapes.