Question by chelder · Apr 13, 2018 at 09:10 PM · position coordinates geometry

Getting position of a coordinate on the surface of a sphere

So I want to create a object B close to another object A, but I'm trying to avoid that A covers B:

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I have thinking how to achieve that. Take a look of the following drawing:

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I have been thinking in a solution in a math - geometry way before searching for some Unity3D function to solve the problem. I have realise A and B would be on the same surface if the camera is within a sphere with radius c-A. So I guess the solution can be related to get a point at a B at a distance A-B from A on the surface of the sphere with radius c-A. Does it has sense? Any other idea? How to do it with maths and Unity?

asset-2.png (8.9 kB)

asset-1.png (9.4 kB)

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elenzil · Apr 15, 2018 at 03:33 AM 0

let's simplify and say that the camera is the origin. ie, the camera is 0,0.

assuming that, is this what you're after ?

given: ptA - the center of circle A radiusA - the radius of circle A * radiusB - the radius of circle B

and you want to find: * ptB - the center of circle B, such that ptB is the same distance from the origin as ptA, and so that circle A and circle B barely touch.

without further constraints, these conditions are impossible to satisfy for all values of ptA, radiusA, radiusB. for example if ptA is say [1, 0] and radiusB is 10000000 then you can't place circle B at the same distance as circle A without them overlapping.