folks who have done games with non-flat planets:
it it annoying doing physics, collision, alignment etc. if you use world coordinates rather than some sort of more gridwise local system with actually flat ground?
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Fun fact: One of the prototypes for XCOM: The Bureau let you fly and dogfight around the entire earth. IIRC I ended up using quaternions a lot, eg 1 quaternion + a height float to represent position.
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Do you remember how you represented heading along the surface of the sphere? That's something that's tripped me up with quaternion+height representations in the past :(
I think I've now been thinking that instead of a bearing angle, you need a vector that represents the plane of the great circle that your entity is travelling along.
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This was all 10+ years ago, but I think heading was part of that same position quaternion. I imagined it as a ship at the centre of the planet, with the q fully describing its orientation there, then offsetting it by a given distance in its local "up" direction.
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Ohh, so the position on the surface of the sphere was based on how the ship was rotated in 3D using the quaternion? Interesting!
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