New star generator for other galaxies... (work in progress)

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Cham M
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Re: New star generator for other galaxies... (work in progre

#101by Cham » 14.09.2011, 17:53

A test version for the most luminous stars, in M33. I find it pretty nice. The HR plot is too homogeneous, though...

There are 20 000 stars in this case, and I'm using the "scaled disk" rendering of stars to see them more easily.

M33a.jpg
M33c2.jpg
M33b.jpg


I'm beginning to think about galactic arms, since with very luminous stars, it could be interesting...

I'm still waiting Fridger's response, about the function used to define the galactic arms (galactic templates)...
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Cham M
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Re: New star generator for other galaxies... (work in progre

#102by Cham » 14.09.2011, 18:17

About the arms, I'll play with the classical logarithmic spiral. However, there are lots of possibilities with the three parameters which defines the logarithmic spiral (in parametric form) and I need to know what Celestia is using to draw its spiral galaxies :

spiral.jpg


EDIT : Mathematica has the ability to superpose a picture and a mathematical curve. So I could easily find the best match, while playing with the curve parameters (in this case, M33).

spirales.jpg
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

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Re: New star generator for other galaxies... (work in progre

#103by Reiko » 15.09.2011, 05:42

When is this ready for use?? :D :D

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Re: New star generator for other galaxies... (work in progre

#104by t00fri » 15.09.2011, 08:11

Cham wrote:I'm still waiting Fridger's response, about the function used to define the galactic arms (galactic templates)...

The templates were NOT produced by means of an analytical math formula. This would not look realistic in the end, since also between the arms some "glowing" material is required. On average, logarithmic spirals are of course the simplest mathematical approximation for the shape of the arms.

The templates are quite complicated to do, requiring a lot of experience how the code associates sprites of a large range of sizes to the pixels on the template. I did all templates by hand (Gimp) in multi-layer technique. A number of layers are the same for each template, as noted by my friend ElChristou (Christophe).

The basic shapes are obtained from an overlay with reference photos that first need to be reprojected to exact face-on view. A crucial aspect are the various brightness levels of the pixel "noise" in-between the arms. The template size is 128x128 pixels.

[ In Celestia.Sci the templates for spirals are much improved and the elliptical galaxies are entirely computer generated with dedicated shader code.]

Cham wrote:I need a list of all spiral galaxies within 10 millions LY ! Someone ?

My galaxy database (galaxies.dsc) in the Celestia distribution comprises ALL galaxies (including dwarfs) within the Local Group volume V <~ (10 Mpc)^3. That should do, right?

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Cham M
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Re: New star generator for other galaxies... (work in progre

#105by Cham » 15.09.2011, 10:24

t00fri wrote:On average, logarithmic spirals are of course the simplest mathematical approximation for the shape of the arms.

I intend to use the logarithmic curves (blurry version, actually) to dispose some stars over the quasi-homogeneous (radial) distribution. That should do it.

t00fri wrote:My galaxy database (galaxies.dsc) in the Celestia distribution comprises ALL galaxies (including dwarfs) within the Local Group volume V <~ (10 Mpc)^3. That should do, right?

Actually, there aren't much spirals in this volume, I think (Milky Way, M31 and M33), unfortunately (or fortunately ?).

Fridger, you didn't responded to my pm yet ?
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Re: New star generator for other galaxies... (work in progre

#106by t00fri » 15.09.2011, 11:32

Cham wrote:Fridger, you didn't responded to my pm yet ?

Didn't arrive here. Typo?

If you have attached an executable file (...zip,...), it will be resent to you.

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Cham M
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Re: New star generator for other galaxies... (work in progre

#107by Cham » 15.09.2011, 11:36

t00fri wrote:
Cham wrote:Fridger, you didn't responded to my pm yet ?

Didn't arrive here. Typo?

If you have attached an executable file (...zip,...), it will be resent to you.

Fridger

????!!!???

I'm sending it back to you... in 2 min.

EDIT : please check your pm...
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

Cham M
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Re: New star generator for other galaxies... (work in progre

#108by Cham » 05.10.2011, 19:59

Today, I built an STC file of 1 MILLION stars for M31 (Andromeda galaxy). The STC file is 138.3 MB in size and Celestia takes about 1 minute to load.

The star search is pretty laggy, but the 3D view is absolutely spectacular, especially with a sprite based nebula (arms) ! :mrgreen: :D :mrgreen: :D :mrgreen: :D
The stars are following the M31 arms structure.
1million1.jpg
1million2.jpg


With the Magnitude pushed to the max :
1million3.jpg
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

Cham M
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Re: New star generator for other galaxies... (work in progre

#109by Cham » 05.10.2011, 20:09

Here's the cross-section of an arm, in M31. The nebula visible on the left isn't the default one. It's a sprites based model superposed on the default representation (the default representation is OFF, in the view below), and truly looks like a real picture ! The frame rate is surprisingly high on my 2009 Mac mini (with 1 million of stars !?!).

1million4.jpg


EDIT : Here's a small video of the 1 million stars distribution. The video is a bit laggy because of the screen capture utility...

http://fsgregs.startlogic.com/Public_Fi ... es/M31.mov
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

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Re: New star generator for other galaxies... (work in progre

#110by Spaceman » 08.10.2011, 21:05

3 years ago I tried to fill the Milky Way galaxy with stars, but the project was finally abandoned. It is possible to use the new star generator for our galaxy as well? :o
"Any sufficiently advanced extraterrestrial intelligence is indistinguishable from God"
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Cham M
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Re: New star generator for other galaxies... (work in progre

#111by Cham » 08.10.2011, 22:59

Spaceman wrote:It is possible to use the new star generator for our galaxy as well? :o

Of course. However, I don't want to build a stellar distribution for our Milky Way, to not interfere with the realistic stars there. Maybe for the unknown "quadran" behind the MW's galactic core, one of these days, but I think there's enough stars available in other galaxies (M31, M33, NGC 404, ...). See this topic :

viewtopic.php?f=23&t=16626
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

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Re: New star generator for other galaxies... (work in progre

#112by Reiko » 09.10.2011, 05:44

When is new star generator to be available? :)

Cham M
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Re: New star generator for other galaxies... (work in progre

#113by Cham » 09.10.2011, 13:30

Reiko wrote:When is new star generator to be available? :)

It will never be available. It's a Mathematica code. I'm releasing its output STC files only.
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

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Re: New star generator for other galaxies... (work in progre

#114by Spaceman » 09.10.2011, 16:19

Cham wrote:
Spaceman wrote:It is possible to use the new star generator for our galaxy as well? :o

Of course. However, I don't want to build a stellar distribution for our Milky Way, to not interfere with the realistic stars there. Maybe for the unknown "quadran" behind the MW's galactic core, one of these days, but I think there's enough stars available in other galaxies (M31, M33, NGC 404, ...). See this topic :

viewtopic.php?f=23&t=16626

Having stars with fictional planetary systems in other galaxies is something always welcomed. I'll grab them too very soon :D :D
However I'm sure that not everybody cares about realism, when it's about having stars in our galaxy as well. Sure having a red giant 1 light year from the Sun is not the best :lol: , but still it can be very useful for world builders and science fiction writers :D . Just my 2 cents...
"Any sufficiently advanced extraterrestrial intelligence is indistinguishable from God"
Michael Shermer

My addons:
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