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Celestial Grid

By Dave, 7 February 2010 00:01
Posted in Virtual Universe

To make things much easier, I wanted to render a grid to help with orientation. In planetary terms this would be a latitude/longitude grid, however the celestial equivalent is declination/right ascension respectively.

This was simply a matter of drawing line primitives on the surface of a sphere centered around the camera viewpoint. I chose not to converge all my lines of right ascension at the "poles", as shown below. The only drawback to this was that I had to draw multiple lines, since it's only possible to use just one if the lines converge.

Celestial Grid Equator

Figure 1. Celestial Grid Equator

Celestial Grid Poles

Figure 2. Celestial Grid Poles

One advantage of using multiple lines, however was that I have the option of varying the color for particular lines. For example, I might choose to make the "equator", or elliptical plane, more opaque.

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