Spherical grid coordinate systems

Progress has been better than expected and spheric grids are practically done. This is a good opportunity to take a look at the coordinate systems in spheric grids.

The first application for spheric grids that came to my mind was using them along the surface of a planet. The coordinate system used for navigation on Earth is called the geographic coordinate system, a point is identified using its altitude (distance from the planet's surface), the longitude and the latitude.

The latitude is the angle between the vector and the equatorial plane, the longitude is the angle between the vector and the plane of the prime meridian. This coordinate system has signed coordinates: points beneath the surface have negative altitude, the southern hemisphere has negative latitude and the western hemisphere has negative longitude.

The other coordinate system is spherical coordinates. This time we use the distance from the origin of the grid, the polar angle between the vector and the polar axis and the azimuth angle around the prime meridian.

This coordinate system has no negative coordinates: the polar angle at the equator is π/2 (90°) and moving south increases the angle up to π (180°) at the south pole, the azimuth angle works like polar coordinates and wraps around after a full circle.

There is also the grid coordinate system, it is the same as spherical except that coordinates are given in relative grid lines rather than absolute distance and angles.

Update coming soon

So far everything looks in order, I plan on submitting the update this week if everything goes well. I still have some more testing to run before I can declare it production ready, then it's up the Asset Store team. Spheric grids have been on the to-do list since the very start, so seeing them finally make it into Grid Framework is a big step for me and I am looking forward to seeing them in your games.