Planetary Nebula models (sprites)

[Cham]

Here's another prototype, at the M1 Crab location. It matches very well my old M1 billboard :

CrabA.jpg

The pulsar is right there in the middle.

The colors are beautifull, but I'm not sure they are relevant for the Crab nebula.

CrabB.jpg

CrabC.jpg

There's still an issue with the sprites density, at the intersection of filaments, and I don't know yet how to solve this.

[Cham]

Wow ! Even with this crude model, the view from inside the nebula is really spectacular !

Here's the central pulsar, with its relativistic magnetic field (simple dipole rotating) :

CP1.jpg

CP2.jpg

CP3.jpg

If only I could improve the density problem at filaments intersections...

EDIT : Here's a small addon to try. Notice that this is just a preliminary version. The model has some small defects I want to fix.
This addon doesn't include the pulsar and its magnetic field.

http://fsgregs.startlogic.com/Public_Fi ... abTest.zip (365 KB)

[Cham]

I already have some ideas for large Orion-like nebulae. I'll work on this after I'm satisfied with the supernova remnants.

Random walk can define some disordered and "natural" looking curves. I could add a random thickness to each curve and blurr it, so to produce the structures we may see in most large nebulae. Here's a set of random walk curves in Mathematica :

randomWalk.jpg

With a star field inside, it could be spectacular ! I'm sure this could be done. Hmm, later, ...

[t00fri]

Cham,

did you try blending your random walk strings with Perlin noise backgrounds? I use the very flexible 2D Perlin noise for irregular galaxy rendering etc. Here is a small example:

perlin.jpg

You can easily generate Perlin noise within your Mathematica box as well.

F.

[Cham]

Fridger,

no, I didn't blurred the random walk yet. This is a project for the following months.

For the moment, I need to concentrate on the supernova remnants (Crab-like nebulae).
I still have an issue with sprites density at the tree-like intersections, which gives an un-natural rendering in Celestia (too much sprites at the intersections).

[t00fri]

Fridger,

no, I didn't blurred the random walk yet. This is a project for the following months.

For the moment, I need to concentrate on the supernova remnants (Crab-like nebulae).
I still have an issue with sprites density at the tree-like intersections, which gives an un-natural rendering in Celestia (too much sprites at the intersections).

I didn't mean to blurr the random walk strings. Rather your sharp strings might look great if embedded in a "cloudy" Perlin noise background...especially e.g. in case of Crab modelling.

F.

[t00fri]

Here is a 5min exercise with GIMP of what I have in mind:

• I used your above strings and moved the black background to alpha, which makes your randomWalk image transparent. This looks about like so (after rescaling to the size of my Perlin noise image above:
  
  
  strings.png
  
  
  
  Sorry this box doesn't render transparent backgrounds. So white <=> transparency...
  
  
• next I blend it with my Perlin noise in "Lighten only" blend mode. Then the result already looks quite neat I think:
  
  
  perlin_blend.jpg

All this can very easily be coded in C++ + OGL ...

F.

[t00fri]

or just to carry on a bit towards a more Crab-like coloration etc...
[click on image by all means!]

crab.jpg

F.

[Cham]

The background fog may be tricky in Celestia : Since there are several large sprites, they will add and make rendering confused.
I did tried before, for my planetary nebulae. The effect isn't very satisfying.

Even if the sprites are smaller (and more numerous), the fog effect will not be very convincing in Celestia.

There's a limitation of the sprites technique (at least on the addon front, with the current implementation of sprites).
The choice of blending modes is too limited.

I'll try again, but I'm pessimistic. I don't think I could achieve a nice "fog-like" effect with simple sprites.

[Cham]

or just to carry on a bit towards a more Crab-like coloration etc...

About the colors, what palette do you suggest to me for the Crab ?
I can't trust the various pictures on the internet ; they are all false or exagerated colors.

I need three RGB colors : center (approximately blue), middle (approximately green), and exterior (approximately red).
Which values ?

[t00fri]

The background fog may be tricky in Celestia : Since there are several large sprites, they will add and make rendering confused.
I did tried before, for my planetary nebulae. The effect isn't very satisfying.

Even if the sprites are smaller (and more numerous), the fog effect will not be very convincing in Celestia.

There's a limitation of the sprites technique (at least on the addon front, with the current implementation of sprites).

I'll try again, but I'm pessimistic. I don't think I could achieve a nice "fog-like" effect with simple sprites.

The blue "cloudy" Perlin noise image above WAS actually a screenshot from celestia.Sci. Of course, I did NOT render the Perlin noise with the usual (extended) 2d texture sprites that you use.

One can even make random strings with Perlin noise, actually. Perhaps I'll start a thread in CM these days about such techniques. Perhaps, there will be some fruitful discussion in an absolutely "StarTrek free" environment

F.

[t00fri]

or just to carry on a bit towards a more Crab-like coloration etc...

About the colors, what palette do you suggest to me for the Crab ?
I can't trust the various pictures on the internet ; they are all false or exagerated colors.

I need three RGB colors : center (approximately blue), middle (approximately green), and exterior (approximately red).
Which values ?

Unfortunately that cannot be answered in a few lines. I am working since ~ 6 months on a thorough framework of implementing consistently color degrees of freedom into visualization within celestia.Sci. This involves first of all color managed monitors and then special color profiles for each astronomical instrument (filter set) that is of interest ( SDSS, Hubble,...). Like in normal color management, these profiles lead to well-defined transformations in color space, mapping e.g. from SDSS color to Hubble etc. Without such a complex framework, coloration of the Universe remains a rather random affair.

In multi-wavelength astronomy, the color space is of course much larger than usual since it includes UV and IR regimes that will be mapped onto RGB for visualization via the instrument-profiles!

F.

[Cham]

Without such a complex framework, coloration of the Universe remains a rather random affair.

Then I'll use approximate colors from the most popular pictures...

The final constraint will be the rendering beauty of the model in Celestia.
It would be comparable to the artistic interpretations we can find everywhere.

Anyway, the 3D distribution morphology is also very approximate. My models are just generic representations.

[t00fri]

That sounds like the best procedure, certainly in this more exploratory stage.

F.

[Cham]

Hmmm, I already see "the pillars of creation" in there (M16).
This is promising too.

pillars.jpg

I may be very active, in the following months. Lots of new ideas with Mathematica, to "sculpt" some nice sprites..

[Cham]

Another nice one (if only I could solve the density problem... )

rem1.jpg

rem2.jpg

The view from the inside is really spectacular !

rem3.jpg

This could give an idea of what it may look **inside** the crab nebula. A simple picture can't show this !

[Fenerit]

These sprites are amazing. I tried your tests: woundrous. As for the density problem, maybe something which can set their opacity toward 0 whether unable to decimate points. An analysis tool for points' distribution and its decimation? Erasing points through a 3D modeler?

[Cham]

Just an experiment. It's beautifull in Celestia, but doesn't feel like a nebula :

exp1.jpg

exp2.jpg

I still have the density problem (it's particularly evident in these pictures).
I'll try adding a short range repulsive force, but it will probably slow down the code execution a lot.

EDIT : Actually, I need to add a constraint on the distribution of points : the shortest distance between two points shouldn't be smaller than the local sprite size.

[Hungry4info]

These are definitely incredible. Your latest images remind me of the structure of galactic filaments. Keep up the good work.

[Cham]

Actually, I need to add a constraint on the distribution of points : the shortest distance between two points shouldn't be smaller than the local sprite size.

I think I've found it ! Thanks to the helpfull folks at the Mathematica forum !

The Mathematica code is now generating nice models, without too much sprites overlapping !
Get ready for an avalanche of supernova remnants !