Long story short: I would like to compute intermediary points on the circle delimiting the "front half-sphere" (the one rendered by the camera).
We have :
- a red sphere centered on 0,0,0 of radius 1
- a black circle of radius 1 and always centered on 0,0,0. So this circle can be any big circle of the sphere.
- An blue arc BD on the sphere surface (here there are 3 arcs but the question is only for one). The arc is only known by its points B and D, only the shortest arc between these points is interesting.
Want I need : the coordinates of point H, intersection of arc BD and the black circle.
I only have basic trigonometry knowledge (I forgot almost all my math courses !) and I can't get my head of this and find where to start...