star textures

[dalmatian_fanatic]

i notice that there are several different star type textures in celestias texture folders, like A, B, G. But i notice that unless you specify in the STC's, celestia gives ALL of the stars in celestia the A star texture. Is there a way perhaps to get Celestia to associate the textures with the stars spectal type? Otherwise, why even have the other textures in the first place?

[selden]

The separate surface textures are still included due to an oversight, I suspect. Celestia used to use different surface textures to provide appropriate coloration, but reverted to using only one when the star illumination code was changed to use the SpectralType field to determine the colors used for stars' images.

There have been some theoretical studies which suggest that stars of different stellar classifications may have different kinds of surfaces (which might justify different surface textures), but the evidence seems to be inconclusive.

You can specify a specific surface texture image for a particular star if you create an STC catalog for it and specify a Texture. A description of the STC parameters that became available starting with Celestia v1.4.0, including the Texture parameter, is at http://www.lepp.cornell.edu/~seb/celest ... eters.html

[Cham]

I think it's MUCH preferable to use a star textures set, like before, than using the same lame texture for ALL the stars. Stars lost their "personality" or "individuality", since 1.4.1. They are boring ! Also, the texture used doesn't match the atmosphere color at all. They are all looking white, while their atmosphere has a different color.

[dalmatian_fanatic]

im glad someone else shares my opinion of the stars, if only there were an addon/plugin to make for celestia to be able to use the textures like before(it'd be way too time consuming to edit all of the STC's, and then trying to comprehend the jibberish of the Stars.DAT file)

[buggs_moran]

I'd agree. Although I am not an astrophysicist, I have read/seen some info on stars like Betelgeuse with large granulation patches compared to the sun...

The scale of photospheric convection in red giants is generally associated, by analogy with the Sun, with the atmospheric pressure scale height and the thickness of the superadiabatic transition layer. As pointed out by Schwarzschild (1975), both of these quantities are relatively much larger in terms of the stellar radius in a red giant than in the Sun. On these grounds, Schwarzschild concluded that only a few cells must be present on a red giant surface, in contrast with two millions cells observed on the solar surface. Observations of brightness variations in the TiO band on Betelgeuse (Gaustad 1986) and direct imaging of Betelgeuse (Gilliland & Dupree 1996) with HST have yielded results that are compatible with giant cells, although other interpretations (e.g. pulsation) are possible. 2D numerical simulations (Freytag et al. 2001) also claim compatibility with the giant cell interpretation.

[rthorvald]

You can specify a specific surface texture image for a particular star if you create an STC catalog for it and specify a Texture. A description of the STC parameters that became available starting with Celestia v1.4.0, including the Texture parameter, is at http://www.lepp.cornell.edu/~seb/celest ... eters.html

Selden, i tried to do this here according to your description. but it does not work. Am i misunderstanding something, or doesn??t it work with 1.5?

Code: Select all

297297 "Ran:The Billow Maidens"   {
   Texture   "th_00_ran.*"   
   RA 270.674708333333   
   Dec -23.1049444444444   
   Distance 5229.982   
   SpectralType "G2 V"   
   AppMag 15.9
   }


- rthorvald

[selden]

Strange: your stc works for me under Windows, although I had to specify a different surface texture image, of course.

Are there any error messages in the console log?
Check for typos, of course, and that the specified image file is in one of the textures subdirectories.

[chris]

Usually there are no spaces in the spectral type, so "G2V" rather than "G2 V". That might be confusing Celestia, though I don't understand why it should work for Selden.

--Chris

[rthorvald]

Strange: your stc works for me under Windows, although I had to specify a different surface texture image, of course.

Are there any error messages in the console log?
Check for typos, of course, and that the specified image file is in one of the textures subdirectories.

I have checked for these things. Everything appears normal. The log shows no trace of the texture being loaded, but there are no error messages either...

Usually there are no spaces in the spectral type, so "G2V" rather than "G2 V". That might be confusing Celestia, though I don't understand why it should work for Selden.

I fixed this. No change...

Might there be a bug in the 1.5 pre2?

- rthorvald

[chris]

Odd . . . it seems to be working for me (with a different texture of course.) Have you tried it with one of the standard Celestia textures, e.g. io.jpg?

--Chris

[rthorvald]

Odd . . . it seems to be working for me (with a different texture of course.) Have you tried it with one of the standard Celestia textures, e.g. io.jpg?

Yes, i tried with the default earth.png. It does not work with different textures, and it does not work with neither PNG or DDS textures...

- rthorvald

[rthorvald]

I have localized the problem: the path to the image file is broken!

1) When the stc file resides in the "data" folder, the texture does not load.

2) When i move it up to the parent dir, it loads!

- rthorvald