To me the feeling of over enlightening from the center is a question of tuning, if Fridger is able to add some more "dust" all over the template this impression will disappear.
I think I don't have overlighting from the center. Moreover, for anyone who thinks that I do, I have implemented a sophisticated key adjustment that is able to tune smoothly BOTH the central galactic lighting strength AND the brightness of the field stars in the environment. The trick is that the central galactic brightness varies periodically between its minimal and maximal value, while the star brightness increases/decreases monotonically if the familiar keys ']' and '[' are pushed. This gives a most convenient and flexible single key adjustment of all critical lighting parameters!
Same for globular clusters, actually.
But again Fridger, how is defined the base sprite (blob)? An alpha attribute for the diffuseness and a single tone (related to the brightness data from the template), right?
I am not sure what you really want to know here. Also I don't know how to answer precisely without using complex formulae and specialized OGL terminology.
I have tried to be precise in my previous post already
. First, there are the points that are read from the template. They contain the morphological info about the galaxy as well as the associated brightness values for each galaxy point. The Blob structure is like so:
unsigned int colorIndex;
ranges from 0..255 and maps the radial distance of the Blob from the galaxy center to a particular color.
Next a rgb color vector is built up as a linear superposition between orange and blue tones, depending on the profile used (e.g. SDSS type). The actual mixture depends on the B-V data and the radial position in the galaxy (<=> colorindex).
Next the alpha value is composed that includes as factor the original brightness values and various other specialities. All this is transferred to the GLSL fragment shader , where the rgb color is modulated with a procedural sprite texture that is centrally peaked as I previously described.
There is actually another new pair of keys '(' and ')' that allow to adjust the rgb color saturation
with everything else fixed. This allows to switch to grayscale
rendering of galaxies and globular clusters everywhere or by default only at small scale (<=> visual observation!), along with various other more complex tunings.