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PostPosted: Wed, 12-02-14, 15:49 GMT 
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And finally two nice views of the New from Old model shown in the noise example above :
Attachment:
NewOld1.jpg
NewOld1.jpg [ 174.31 KiB | Viewed 2695 times ]

Attachment:
NewOld2.jpg
NewOld2.jpg [ 185.94 KiB | Viewed 2695 times ]

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PostPosted: Wed, 12-02-14, 21:34 GMT 
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I decided to move my progress reports about DLA-based rendering of Irregular Galaxies to the celestia.Sci Development forum,

viewtopic.php?f=11&t=628#p12061

since these constitute an important development aspect of celestia.Sci.

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PostPosted: Sun, 16-02-14, 21:35 GMT 
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Just had an idea :

instead of defining real stars in Celestia, I could define them as glowing sprites directly in the nebula model instead.

Here's a prototype, in the last galaxy of Celestia's database !
Attachment:
stars1.jpg
stars1.jpg [ 180.03 KiB | Viewed 2644 times ]

Attachment:
stars2.jpg
stars2.jpg [ 109.21 KiB | Viewed 2644 times ]

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PostPosted: Sun, 16-02-14, 22:06 GMT 
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Quote:
instead of defining real stars in Celestia, I could define them as glowing sprites directly in the nebula model instead.


Yes, but I am afraid that it will be hard to render very faint stars that just appear as needle-fine points. The latter is no problem when using shaders. It's a pity you don't speak C++ ;-)...

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PostPosted: Wed, 26-02-14, 15:18 GMT 
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While building some supernova exploded shells, I may have found a new way to generate some nice irregular nebulae.
I'll have to study this a bit.

Here are two exploded shells (the second one is just a simple variation of the first) :
Attachment:
shells.jpg
shells.jpg [ 224.49 KiB | Viewed 2610 times ]


I could then zoom on the shell (or enter it), and extract a very small part to build new irregular nebulae. Adding more "custom home made" noise would add more details in it :
Attachment:
shells_extract.jpg
shells_extract.jpg [ 157.66 KiB | Viewed 2610 times ]


Three small parts of the same shell that may be very interesting as irregular nebulae :
Attachment:
extractions.jpg
extractions.jpg [ 230.74 KiB | Viewed 2610 times ]

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PostPosted: Thu, 27-02-14, 14:14 GMT 
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The idea above is working, but I'm not sure I'll exploit it to its full potential.
The global distribution is completely different than the other nebulae models I've made before.

Here's a proof of concept prototype. Extraction of a small detail in the exploded shell shown above, with some noise added :
Attachment:
extract1.jpg
extract1.jpg [ 109.62 KiB | Viewed 2593 times ]

Attachment:
extract2.jpg
extract2.jpg [ 124.11 KiB | Viewed 2593 times ]

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PostPosted: Thu, 27-02-14, 14:27 GMT 
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Oow ! The same prototype with a different rendering gave some very nice results ! This kind of sprite rendering is usually bad for nebulae, but in this case it is MUCH better than the usual blend add option :

Three views of the same extract :
Attachment:
extract3.jpg
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Attachment:
extract4.jpg
extract4.jpg [ 97.27 KiB | Viewed 2591 times ]

Attachment:
extract5.jpg
extract5.jpg [ 85.83 KiB | Viewed 2591 times ]

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PostPosted: Thu, 27-02-14, 14:48 GMT 
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Hmm, I think this is interesting. More like "cold/dark dust" nebulae :
Attachment:
test1.jpg
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test2.jpg
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test3.jpg
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Attachment:
test4.jpg
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Attachment:
test5.jpg
test5.jpg [ 138.72 KiB | Viewed 2589 times ]

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PostPosted: Thu, 27-02-14, 21:30 GMT 
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Could also be great to shape the stellar distribution like a nebula sprites distribution ! ;)

Just a prototype :
Attachment:
stars1.jpg
stars1.jpg [ 106.66 KiB | Viewed 2581 times ]

Attachment:
stars2.jpg
stars2.jpg [ 159.91 KiB | Viewed 2581 times ]

Attachment:
stars3.jpg
stars3.jpg [ 127.13 KiB | Viewed 2581 times ]

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PostPosted: Sat, 01-03-14, 0:58 GMT 
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A new model from the previous idea. Three views :
Attachment:
clouds1.jpg
clouds1.jpg [ 112.23 KiB | Viewed 2555 times ]

Attachment:
clouds2.jpg
clouds2.jpg [ 118.59 KiB | Viewed 2555 times ]

Attachment:
clouds3.jpg
clouds3.jpg [ 128.84 KiB | Viewed 2555 times ]

Feel like very dusty in there. :)

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PostPosted: Sun, 02-03-14, 20:03 GMT 
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Here's another way of rendering irregular nebulae in Celestia. Somewhere inside the LMC :
Attachment:
LMC1.jpg
LMC1.jpg [ 136.21 KiB | Viewed 2536 times ]

Attachment:
LMC2.jpg
LMC2.jpg [ 137.06 KiB | Viewed 2536 times ]

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PostPosted: Mon, 03-03-14, 8:26 GMT 
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Cham, on your last posts, we can see some dark sprites here and there; can you try a ring of these sprites around a nebula to see if the blending is ok to simulate light blocking structure? (->like the dark lane in the galaxies)


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PostPosted: Mon, 03-03-14, 14:50 GMT 
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ElChristou wrote:
Cham, on your last posts, we can see some dark sprites here and there; can you try a ring of these sprites around a nebula to see if the blending is ok to simulate light blocking structure? (->like the dark lane in the galaxies)


Mixing both kind of sprite renderings rarely give good results, because of the absence of depth sorting. In the case shown above, the absence of depth sorting can be seen very easily when we move around in 3D, but it's acceptable in this case (very rare case).

The main problem with ring and shell distributions is the density of superposed sprites when we look through the thick parts. There may be a luminosity problem (with the blend add option), if the opacity isn't low enough, or some ugly artifacts (onion-like bending) if opacity is too low. Without the blend add option, the absence of depth sorting of sprites is very easy to notice. Also, the superposition of both kind of sprites (with and without blending) is extremely hard to control and usualy give some weird rendering. The result strongly depends on the number/density/size of sprites, color/opacity palette, and the global distribution (shape, internal structures...). The number of constraints is very high.

However, there are ways to get some **very** good looking results, despite all the strong constraints and limitations.

Experimentation is the main rule here.

EDIT : The best results are obtained for highly fragmented distributions of sprites (lots of random holes), such that no view could lead to a superposition of many sprites. This tends to avoid the luminosity and depth sorting problems. Big sprites tend to give poor results (luminosity and artifacts problems), so it's preferable to use many small sprites.

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PostPosted: Mon, 03-03-14, 15:42 GMT 
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Just a cool view :
Attachment:
cool.jpg
cool.jpg [ 229.09 KiB | Viewed 2512 times ]


Yesterday, I visited the Apple store. I tested my version of Celestia 1.7.0 on a new Mac with a large 27" screen and also on a MacBook Pro with a Retina display, with OS X Maverick and the Intel Radeon Iris pro GPU. I almost got an erection ! ^^ Celestia's behavior was simply amazing !

I'm now very tempted to buy a new Apple screen to replace my now aging 20". I'll wait the next update, since their screens are long overdue for an update.

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