Nebulae in 1.2.6

[selden]

Thanks!

[jim]

Ras'

Would it be possible for you to publish a .3DS model of a transparent square surface (x=y=1, z=.0001) that can accept any texture image?

Selden, i'm not sure if this is possible. The only model with transparency i know that use a ssc defined map is the black hole. But in this case it's not a true transparency only the diffusse matierial was set to 50% and therefore the hole looks transparent.

Bye Jens

[selden]

Jens,

Well, whether or not transparency is a native characteristic of the model, a simple square object with the same characteristics as the model Ras' created for his NGC 1999 model would be just fine

When one applies to that model any PNG image that has a transparency (Alpha) channel, then one can see through the transparent areas and view objects that are behind NGC 1999.

Unfortunately, that particular model can only be used with a surface texture map that has a specific name (V380_neb.png). That limitation means that one has to have s separate, individual model for each "billboard", each with its own image file. Right now Celestia v1.3.0pre2 does not implement the "Texture" directive in its .DSC files, but I wouldn't be a bit surprised if it gets added soon.

[Rassilon]

Actually hes right selden...Trying this out with a plain billboard 3ds did not work...It has to be set up in Studio Max first as a transparency map...You can however use a HEX editor to change the filename reference in the 3ds file itself...or should be able to...just make sure the new filename is trunicated exactly to the length of the old filename...

Also you MUST use the gimp to create the png files I use for nebulas exactly like this...You have to make a square texture something like 1024 x 1024 and give it an alpha channel of the same image then save as 32 bit tga file...You can do this in the gimp I believe too...load it in the gimp and create a RGBA alpha 0 channel and save as a png file to do this decompose image to rgb click on the alpha 1 image and compose rgba placing all rgb images in proper color schemes then alpha 1 in the alpha channel...when compsed it will produce an alpha 0 transparency map that Celestia will use to render the black transparent when applied to the model...Remember all you have to do is use the HEX editor to change the filename and create the above image as I have instructed and you can easily fill your Celestia with nebula...

Good luck!

[jim]

Selden, i'm conscious of the problem. All what i want say is that your good idea will probably not work because some restrictions in celestia. Celestia use the alpha channel for specular reflection. I think this is also true if you use a 3DS model with ssc file defined texture. I know that the alpha channel is used for transparency if the texture is defined in the matierial of the 3DS file.

Rassilon, i think too the way with the HEX edidor should work.

Jens

[chris]

Unfortunately, that particular model can only be used with a surface texture map that has a specific name (V380_neb.png). That limitation means that one has to have s separate, individual model for each "billboard", each with its own image file. Right now Celestia v1.3.0pre2 does not implement the "Texture" directive in its .DSC files, but I wouldn't be a bit surprised if it gets added soon.

I will add some sort of support for billboarded nebulae . . . However, I'm quite insistent that everything in Celestia be truly 3D, so I'll never include a package of billboarded nebulae in the base Celestia distribution. It could make a worthwhile add-on though.

--Chris

[t00fri]

Unfortunately, that particular model can only be used with a surface texture map that has a specific name (V380_neb.png). That limitation means that one has to have s separate, individual model for each "billboard", each with its own image file. Right now Celestia v1.3.0pre2 does not implement the "Texture" directive in its .DSC files, but I wouldn't be a bit surprised if it gets added soon.

I will add some sort of support for billboarded nebulae . . . However, I'm quite insistent that everything in Celestia be truly 3D, so I'll never include a package of billboarded nebulae in the base Celestia distribution. It could make a worthwhile add-on though.

--Chris

That's precisely why I am still on the sceptical side with the galaxies and nebulae issue in Celestia. Presently, these objects are incorporated in a merely schematic manner which is quite a clever compromise between the lacking accurate 3d info and not including them at all.

So far any celestial object included in Celestia satisfied a very high strandard of scientific accuracy besides being just beautiful or "fun". Explicit, colorful /3d rendering/ of galaxies and nebulae for the first time requires to manifestly abandon this philosophy!

Moreover there does not seem to exist any present scheme for "mass production" of these objects;-). What is it good for to include a colorful "phantasy" NGC 1999 and a few others, but leave out most of the other 10000 NGC's;-) without any underlying logics apart from lack of "manpower" to handycraft them individually?

Based on the plausible assumption that galaxies have a more or less universal ratio of "principal axes", some galaxy catalogues include angular tilt info that may be used to approximately reconstruct the true shape from photographic images. One may imagine to use image manipulation techniques to "unfold" their true "photographic" appearance in their principal axis system, based on scripting like "GIMP-Perl". This seems feasible automatically for a large number of objects (with not too large tilts, of course;-)). One may add universal transparent 3d meshes perhaps to get somewhere...
Along such lines, there might be some progress, perhaps...

Bye Fridger

[Rassilon]

I think we will be ok with a bit of phantasy in creating those nebulas Fridger...Too much accuracy without any positive facts will keep us in the dark so to speak...It is better that we render a fictional representation that appears real from our vantage point on earth to give us a glimpse of what may lie out there...

And yes the lack of individuals as dedicated as I and as well patient at doing what I do doesnt allow for more of these objects sadly...I so desire more individuals who share that same vision I do...because I dont see myself as a 99 year old man still trying to put together the complete galactic addon for celestia

Guess the point we both have made is take it as it comes...

[t00fri]

I think we will be ok with a bit of phantasy in creating those nebulas Fridger...Too much accuracy without any positive facts will keep us in the dark so to speak...It is better that we render a fictional representation that appears real from our vantage point on earth to give us a glimpse of what may lie out there...

And yes the lack of individuals as dedicated as I and as well patient at doing what I do doesnt allow for more of these objects sadly...I so desire more individuals who share that same vision I do...because I dont see myself as a 99 year old man still trying to put together the complete galactic addon for celestia ;)

Guess the point we both have made is take it as it comes...

Ras':

I certainly appreciate your great graphical work on NGC 1999 very much and it really looks beautiful!

The point I want to make is that we should /NOT mix/ the different possible application lines of Celestia:

1) scientific reference + educational etc...

2) browsing space for enjoyment

3) virtual worlds, starwars recreation and the like

Handicrafted nebulae and galaxies along the lines you pioneered, would excellently fit into categories 2) and 3), with numbers NOT implying any ranking from my side!

It is not difficult to provide an appropriate structure in celestia that the separations may remain intact. Remember that Chris has already extended the directory structure for such multi-application purposes...


Bye Fridger

[selden]

Fridger,

You wrote

Moreover there does not seem to exist any present scheme for "mass production" of these objects;-). What is it good for to include a colorful "phantasy" NGC 1999 and a few others, but leave out most of the other 10000 NGC's;-) without any underlying logics apart from lack of "manpower" to handycraft them individually?

Respectfully, I have to disagree with the philosophy implied here.

Where would we be if individuals were not willing to concentrate their efforts on that tiny piece of the universe that their limited resources make avaiilable to them?

[Guest]

Fridger,

You wrote

Moreover there does not seem to exist any present scheme for "mass production" of these objects;-). What is it good for to include a colorful "phantasy" NGC 1999 and a few others, but leave out most of the other 10000 NGC's;-) without any underlying logics apart from lack of "manpower" to handycraft them individually?

Respectfully, I have to disagree with the philosophy implied here.

Where would we be if individuals were not willing to concentrate their efforts on that tiny piece of the universe that their limited resources make avaiilable to them?

Selden:

I think you misunderstand. What disturbs me is to include nearby bright galaxy x,y and z but leave out 500 /equally bright and close ones/. If you do not suffer from such a philosophy, I certainly do;-).

I would not, if we were to include just /all/ the brightest 50 or 100, for example.

Incidentally, we meanwhile know quite a respectable fraction of the universe since it is expanding from a "point" at the time of the BigBang...

So at the time of the decoupling of photons, corresponding to the beautiful cosmic microwave background experiments (CMB, WMAP), the causally connected regions of the universe were only /~ 1 degree/ corresponding to the patch sizes of temperature inhomogeneities we observe today!

Bye Fridger

[t00fri]

Selden:

the mailbox apparently agreed with your above argument and therefore "punished" me by cutting out my name again;-)

Bye Fridger

[selden]

To a certain extent I agree with you, Fridger. Fortunately, Celestia's versatile and rapidly improving add-on capability supports the efforts of one who devotes all his efforts to painting one tiny leaf[1] as well as it supports those who add large populations to the sky.

[1] a reference to one of Tolkien's stories.

[Rassilon]

Well if you really want to get to the facts very little we have is factual about our universe...Most of the data we have is assumptions that these stars or nebula or even galaxies are at the distances implied...As we progress we find new and improved methods in mesuring and calculating those distances...Plotting thier location in the sky is simple...Distance has always been a 'guess' an educated one none the less...

Granted my last efforts with ngc1999 was fictional due to the fact it added a solar system...but should without the phantasy system lie in an educational category just as much as black holes and quasars do...but as hypothetical representations and not science fiction...well I hope thats not me reading incorrectly into what you said...

[t00fri]

Well if you really want to get to the facts very little we have is factual about our universe...Most of the data we have is assumptions that these stars or nebula or even galaxies are at the distances implied...As we progress we find new and improved methods in mesuring and calculating those distances...Plotting thier location in the sky is simple...Distance has always been a 'guess' an educated one none the less...

Granted my last efforts with ngc1999 was fictional due to the fact it added a solar system...but should without the phantasy system lie in an educational category just as much as black holes and quasars do...but as hypothetical representations and not science fiction...well I hope thats not me reading incorrectly into what you said...

Sorry Ras, the mailbox is horribly slow right now over here, and after writing a detailed answer, it kicked me out once more...

Too tedious to start all over again.

Let's say simply: I agree with you;-)...

Bye Fridger

[Buzz]

I wrote this under a different topic, but I think it fits here better:

Here http://vis.sdsc.edu/research/orion.html you will find an impressive animation of the orion nebula; some of the 3D structure is known.

[t00fri]

I wrote this under a different topic, but I think it fits here better:

Here http://vis.sdsc.edu/research/orion.html you will find an impressive animation of the orion nebula; some of the 3D structure is known.

Right. The animation is from the San Diego /Supercomputer/ center, which does not exactly match what you and me have at home...;-)

Bye Fridger

[Buzz]

Unfortunately not! And it is probably a prerendered movie. But two warped surfaces might do the trick.

[Rassilon]

I can model something similar for celestia...its just a wrinkled plane with a transparency applied...nothing major...

[Psykotik]

I can model something similar for celestia...its just a wrinkled plane with a transparency applied...nothing major...

Wowww... If you think it's a feasible work, do it ! A much prettier (if it's possible) nebula than V380 !

If you don't do it for your country, do it for your fans ! (I know, I know, that's not exactly the words to use in this troubled period)