In part 1 I discussed adding support for drawing constellations, boundaries and asterisms, along with their names.
I've now added support for constellation art. Rather than loading individual images for each constellation shown in the camera view, I opted instead to use the same rendering approach as for background filters, which gives on-demand loading at the appropriate level-of-detail. A screenshot is shown below in Figure 1.
The Space Telescope Science Institiute worked with the U.S. Naval Observatory's Library to scan and painstakingly re-touch a set of beautiful engravings from the 17th century Firmamentum Sobiescianum sive Uranographia star atlas by Johannes Hevelius1. In order to use these images, I first needed to align them with the background stars, then re-project them to a suitable format. I opted for an equirectangular projection. Whilst there is almost certainly a choice of tools available for the job, I thought it would be fun to write my own. The result of applying it to Figure 2 is shown in Figure 3 below.
The app will ship with low-res versions of the art, with higher-resolution versions available as an extra. It is, of course possible to use alternative art using the same extensibility model.
1 Image credit the U.S. Naval Observatory and the Space Telescope Science Institute.