How would people like it, if arbitrary stars of globular clusters become selectable and can be visited?
These stars carry no names and are generated stochastically. Yet with some code I can turn them into possible targets for visits...

I made some respective experiments already: this feature would provide an amazing new "sky experience", when landing amidst a globular cluster...

That sort of thing...



Let me know some opinions.

Fridger

My god, it's full of stars!

Well, it looks very pretty. It was already so with just the sprites. Is there a compromise in performance, making them full of real stars on the fly?

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Guillermo Abramson
Bariloche, Argentina

In this earlier thread, I have already presented some views that can be expected:

Imagine the Solar System was part of a Globular Cluster
http://forum.celestialmatters.org/viewtopic.php?t=422

As a "Gedanken experiment" I simply had placed a globular cluster around our solar system. The respective screenshots should give already some feeling about the "sky experience".

My new globular cluster (GC) stars can hardly be compared with my old sprite-based stars from Celestia. Neither as to rendering performance nor concerning their luminous appearance!

Firstly, in celestia.Sci, the GC stars are rendered with the same shader as my normal shader stars, implying that both types merge perfectly as to the spacial distribution of luminosity, apparent star sizes and color. The old sprite stars were not rendered with GLSL shader technology.

Next, for rendering the large amounts of GC stars I am using the most modern (and fastest!) OGL technology , a "VBO = VertexBuffer Object". VBOs allow vertex array data to be stored in high-performance graphics memory on the server side and promote efficient data transfer. This is the optimal solution for rendering large numbers of objects in one go, provided inherent updating constraints on these objects "factorize" in some way.

Of course I have done benchmarks and the new stars are rendered much faster.
But the results (also relative ones) do depend on the abilities of the graphics hardware.

The most striking visual improvements concern the luminosity shapes of the individual star disks. While in close-up view the old sprite stars have a "dull" and blurred appearance, the new shader stars are really "shining" stars. Moreover, due to the different technology, the magnitude range is huge from the brightest down to 25m. Here is a little comparison for the stars of yellowish M 4, both as seen from a closer distance:



The tremendous "shining star" effect is also well visible in this image from the earlier thread I quoted above:


Fridger

Do you anticipate supporting multiple shadows?

Planets near the center of a cluster might be sufficiently illuminated by more than one star, although perhaps not as brightly as a planet in a double-star system.

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Selden

In a first stage I plan to simply enable selection and visits of star systems (planets + moons) that are part of a globular cluster. As you noted, most interesting effects can be experienced due to the star light from several nearby sources that are distributed over large parts of the sky.
While I did not yet think about the concrete code for that second step, I will certainly attempt to enable Celestia's existing multi-source illumination framework for this case. However for more than 5 sources I think that the light will become simply a rather undirected i.e. diffuse illumination, which by itself may be interesting to explore.

Fridger