LaTeX.org

I found one example there which I may be able to manipulate. It has a sphere with a cone intersecting the sphere in a circle. I can draw a couple different circles that way, and then figure out how to make a plane appear to be connected with the circles.

I'll try that, and probably keep looking.

I need to draw a sphere with three intersecting planes. One plane is tangent, one parallel cutting of a piece, and the third plane not parallel, intersecting the two planes at different places. Also, I need to draw a great circle on the sphere. I have googled a lot and can't find a sample that ...