Color encoding is not consistent under different state

[jichengtao]

1, For the rendering method of "RenderableStars": (1) I found that the (part of) stars' color change when I set the state of ("Color Option" as "Color") to the state of ("Color Option" as "Other data" while the "Other Data Column" as "colorb_v"). (For testing purpose, 'scene/digitaluniverse/stars.asset' in which Speckfile stars can be choose only the first 1000.) (2) For the parameter of "Size Composition Option", it is the "Base multiplyer for the final stars' sizes" as described in the documentation file. There are six options for this parameter: "Use Star's Apparent Brightness", "User Star's Luminosity and size", "Luminosity, size, App Brightness", "Absolute Magnitude", "Apparent Magnitude", "Distance Modulus". It is easy to understand to use Absolute or Apparent Magnitude to control the stars' size. But, for the remaining four options, they are not included in the speck file. So, how do they work actually? 2, For the rendering method of "RenderableBillboardsCloud": I know in the ColorOption I can choose what kind of parameters to be encoded the color. But how is the brightness determined?

[alexanderbock]

With the overhaul of the stars/points rendering, we want to have a documentation that explains how to use the different settings