Questions on some settings in the "solarsys.ssc" f

Post #1by **ElChristou** » 06.02.2005, 20:51

Hi,

I have noticed that some members use different settings in the "solarsys.ssc" file in the earth section:

************************

SpecularTexture "earth-spec.*"
Color [ 0.35 0.35 0.5 ]
SpecularColor [ 0.3 0.3 0.35 ]
SpecularPower 15.0
HazeColor [ 1 1 1 ]
HazeDensity 0.3
Radius 6378.140 # equatorial
Oblateness 0.0034

************************

So, question: are the defaults settings still good or need to be update?
Oblateness is normally uncomment... Ok perhaps I will look stupid but... (I take the risk) what is oblateness?

Post #2by **t00fri** » 06.02.2005, 22:14

The word 'oblate' comes from Latin and means flattened or depressed at the poles. The obviously related expression is 'prolate'.

In practical terms, oblateness measures the deviation from a strictly spherical shape. In geometry, one correspondingly distinguishes "oblate and prolate spheroids".

Bye Fridger

Post #3by **ElChristou** » 07.02.2005, 18:37

Tx Fridger,

So for earth, is this setting change something in the visual (0,0034 quite a small value isn't it??) or better let it uncomment?

Is the setting influe the calculation time for maps?

Post #4by **t00fri** » 07.02.2005, 18:48

ElChristou wrote:Tx Fridger,

So for earth, is this setting change something in the visual (0,0034 quite a small value isn't it??) or better let it uncomment?

Is the setting influe the calculation time for maps?

Why "on earth" would you want to uncomment it? We use such a high amount of precision for all planet orbits. Why would you want to vast it??

Bye Fridger

Evil Dr Ganymede · Post #5by **Evil Dr Ganymede** » 07.02.2005, 19:06

The stats for the equatorial and polar radii for Earth (from the NSSDC Planetary Data sheets) are:

Equatorial radius (km) 6378.1
Polar radius (km) 6356.8

So it probably doesn't really make that much difference in practise if you comment out oblateness, if you don't mind that Celestia isn't 100% realistic (which it isn't yet anyway - IIRC we can't even account for precession accurately yet). It DOES make a difference for worlds like Saturn and Jupiter though, which are rather noticeably flattened at the poles.

Post #6by **ElChristou** » 11.02.2005, 21:20

t00fri wrote:
Why "on earth" would you want to uncomment it? We use such a high amount of precision for all planet orbits. Why would you want to vast it??

Bye Fridger

Ups sorry Fridger but I met oblateness uncomment (for earth) in the freshly extracted package of Celestia...

So there is no problem with textures using it, right?

What about my very first question... pleaaase :wink:

(it's not vital but...)