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 Post subject: Irregular nebulae models
PostPosted: Thu, 14-03-13, 1:34 GMT 
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Since Shatters.net is down, I would like to show my latest results in nebulae modeling here, if you don't mind.

I must admit that despite that it's a first experimental model made with my new Mathematica code, the rendering in Celestia is so good that I'm tempted to use this prototype model in my permanent installation :

Image

Image

Attachment:
7_largeneb3_1.jpg
7_largeneb3_1.jpg [ 64.21 KiB | Viewed 6655 times ]


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Image

Image

Image


Last edited by Cham on Thu, 14-03-13, 20:05 GMT, edited 3 times in total.

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PostPosted: Thu, 14-03-13, 7:01 GMT 
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Cham wrote:
Since Shatters.net is down...


For info, Shatters is ok!

For the thumb as always I guess img tag + url of the image + url of the thumb as link...


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PostPosted: Thu, 14-03-13, 12:21 GMT 
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Ok, the pictures are now showing correctly.
As usual, click on them to get a larger view.


More to come...


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PostPosted: Thu, 14-03-13, 20:32 GMT 
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I'll try to describe the creation process with Mathematica. This message is a work in progress and I don't have much time today. So for the moment, here are two pictures from Mathematica, which let me inspect a model before exporting it to Celestia.

Here are some "pillars" (like "The Pillars of Creation", in the Eagle Nebula. See http://en.wikipedia.org/wiki/Pillars_of_Creation) :
Image

Here's the main nebula (pillars would be inside) :
Image

I'll describe what they are later.

These mathematical models are combined together, with different colors and transparency, and different sprite sizes (more parameters to play with !). The variations possibles are really endless !

Here are four views of the mathematical models above, as seen in Celestia (colors are still at the prototype stage). The level of fun and interesting details is just amazing, even with a small CMOD file (this case is just a 1MB ASCII file, for 11319 sprites !).

Global view :
Image

And from the inside :
Image
Image
Image

In this case, I would prefer something more subtle since it's pretty crowded, and I should increase the transparency of the model (this is very easy to do, by editing the CMOD file itself).

More later...


Last edited by Cham on Thu, 14-03-13, 21:04 GMT, edited 1 time in total.

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 Post subject:
PostPosted: Thu, 14-03-13, 20:46 GMT 
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Martin,

thanks for opening this challenging topic here.

Quote:
the picture thumbnail should be smaller, by the way

The Mathematica boxes are just right (note this is NOT shatters.net ;-) ): their original dimensions are 774px × 748px , i.e. above 700px x 700px. The CM macro scales such pictures to what we feel is a nice fitting size of ~700px x 700px, where details can be seen very well. Here we don't use smaller thumbnails.

Fridger


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PostPosted: Thu, 14-03-13, 21:01 GMT 
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I think your nebula images are looking phantastic. Notably if viewed with Firefox in full-screen mode (F11) on a good 24" monitor.

Already earlier I proposed some blending of your "cactus"-like structures with soft Perlin noise renderings, as I use them for irregular galaxies in celestia.Sci.

Let me briefly recall the result from such a 5 minute exercise:

Image

the pink structures are yours the blue nebulous structure is the Perlin noise (a screenshot of an irregular galaxy).

Such blends could serve very well as renderings for pink HII regions in irregular galaxies. Here is a very high resolution photo of the dwarf irregular NGC 4449 (Caldwell-21) in LMC.

Image

Similarly, by changing the Hue of my above blended structure one might observe some similarity with the Crab nebula.

Image

Of course, there is much to be improved, but I think the direction could be very promising...

Mathematically, I suppose your branching string-like structures should be well described in terms of what is called a Markov Chain, with a special subclass being Random Walk stochastic structures.

Markov chains are usually described by Integro-differential Eqs. Is that how you proceed in Mathematica?

Fridger


Last edited by t00fri on Thu, 14-03-13, 21:14 GMT, edited 1 time in total.

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 Post subject:
PostPosted: Thu, 14-03-13, 21:11 GMT 
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I just noticed that my full size pictures aren't the same as the ones I've uploaded. I get 1600 X 1000 pixels images, while the originals that I've uploaded are 1680 X 1024. Not a big difference, but anyway...


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 Post subject:
PostPosted: Thu, 14-03-13, 21:18 GMT 
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Cham wrote:
I just noticed that my full size pictures aren't the same as the ones I've uploaded. I get 1600 X 1000 pixels images, while the originals that I've uploaded are 1680 X 1024. Not a big difference, but anyway...


Martin,

I suppose this is due to the fact that for the upload macro the maximum original size is 1600x1200. Since your originals are exceeding this limit slightly, some minor clamping to 1600x1000 took apparently place...

Fridger


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 Post subject:
PostPosted: Thu, 14-03-13, 23:21 GMT 
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Cham, this is very good, very nice and very promising. Thanks for sharing it.

I think that a mixture of scales in the structures (along the lines that F suggests) will add a lot of realism.

Guillermo

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 Post subject:
PostPosted: Fri, 15-03-13, 2:12 GMT 
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I made another irregular nebula, similar to the previous one, and I think it's really beautifull. I tried to render some cold clouds of dust. It's not perfect (not opaque enough), but it's pretty anyway.

Here's a 1min 47sec video (13.4MB), for a better feel of its rendering in Celestia, since it's all 3D and volumetric. A picture doesn't do justice to this kind of stuff. Ttake note however that my screen capture utility is slow and the image resolution doesn't do justice to Celestia's rendering.

http://fsgregs.startlogic.com/Public_Fi ... ebula3.mov

It's really fun to move inside and all around, feeling the clouds of dust and gaz all around your head. :shock:

I feel that I'll make dozens of such nebula and start populating the whole galaxy (or maybe just some far away galaxies, like M31 and some others, since I don't like to interfere with known stuff in the Milky Way).

I will have to play also with the colors. There are too much parameters to play with :? , it will take a lot of time to get bored with this !


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 Post subject:
PostPosted: Fri, 15-03-13, 12:42 GMT 
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Here's a quick test, without any internal structures (pillars).

Image
Image

I defined the sprite size according to four choices :

1. Sprites small in the middle, and large at the exterior (linear function).
2. Sprites large in the middle and small at the exterior (linear function).
3. Sprites small in the middle, large at half size of the distribution, and small again at the exterior (quadratic function).
4. Sprites large in the middle, small at half size of the distribution, and large again at the exterior (quadratic function).

The example above was made with choice 4, while all other models I've shown were made with choice 1.

The nebula style is completely different, depending on the choice of sprites size distribution.

The colors and opacity are defined by an independant function. The global shape is defined by the number of random arms and size of arms (random walk curves), etc. And to these, I have to add the smaller structures (pillars and filaments).

So there are so much parameters and variations possible, I could play with this for MONTHS before being satisfied with a collection of nice models. I hate this ! :x

When there's a symetry (as for my spherical planetary nebulae) it is much simpler to generate nice models.

Now, I'm lost in my parameters space ! :evil:


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 Post subject:
PostPosted: Fri, 15-03-13, 14:33 GMT 
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I saved a family of five irregular nebulae, with some internal structures (pillars). They look like the Magellan clouds.

Image

I'll try combining them togther, to make a larger nebula.


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 Post subject:
PostPosted: Fri, 15-03-13, 15:36 GMT 
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And now the fun begins ! Oh my !

Once we have a family of simple models (all the examples above), we can easily scale, rotate, translate and add the models together using a simple spreadsheet app (Excel, NeoOffice, ...). Of course, this could also be done at the DSC file level.

We then get a very rich and highly detailed nebula.

This adds much more combinations and variations possible :x

Here's what I get with two of the models shown above :
Image
Image


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 Post subject:
PostPosted: Fri, 15-03-13, 17:24 GMT 
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Just an inspiring picture of a real nebula. The color palette I'm using matches this one !

Image

What a marvel !


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 Post subject:
PostPosted: Fri, 15-03-13, 18:36 GMT 
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Just a few examples of filiamentary Perlin noise structures that appear to represent suitable substructures for e.g. modeling the above nebula:

For a better comparison, here are two small cut-outs from Cham's marvellous Tarantula nebula image above:

ImageImage

Here is a selection of filiamentary Perlin noise images:

Image
Image
Image
Image
Image

These filiamentary Perlin noise structures may also serve to model the large scale filiamentary structures of galaxies (see e.g. SDSS)

Fridger


Last edited by t00fri on Fri, 15-03-13, 19:07 GMT, edited 2 times in total.

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