Starting-Off

Hi all,

while preparing the transition of celestia.Sci to public access, I happen to encounter some cute screenshots based on new features here and there. . Perhaps it's not useless if I share these now...

Throughout, the displays of solar system bodies correspond to 16k VT textures, ALL compressed with the appropriate DXT format (via my texure tools). Normalmaps are always in the dedicated dxt5nm format, which is crucial!

Moreover, the displays are based on totally stable 64bit code (Windows 7..10, MAC OS and Linux), Eigen 3.3.x etc.

Note that thanks to the DXT format the display is absolutely smooth with fps rates between 50 ..100!

For all screenshots, click on images and then hit the fullscreen key (F11 for FF)

1) Earth and MilkyWay:


2) Irregular galaxy DDO 82 and three bright stars


More to come;-)

Enjoy,
Fridger

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Dock Widgets' Action

Here are some hires celestia.Sci displays (16k, DXT format) of Pluto in Natural color. I have also opened the two Qt DockWidgets (Preferences & (Celestial Browser + Eclipse finder)). In fullscreen mode, they may be moved around smoothly, while in windowed mode they are located in the left and right sections of the window, respectively.

[For all screenshots, click on images and then hit the fullscreen key (F11 for FF)]

1) Fullscreen mode (1920x1080 px) with both Dockwidgets open
Note the toolbuttons appear when the cursor moves towards the bottom lines


2) Fullscreen mode (1920x1080 px) with both Dockwidgets closed
Note the toolbuttons appear when the cursor moves towards the bottom lines


3) Windowed mode (CelestialBrowser Dockwidget open)
Note the toolbuttons that are activated have a blue frame!


4) Windowed mode (only Preferences Dockwidget open)
Note the toolbuttons that are activated have a blue frame!


Finally, the blue halo of backlit Pluto using the parameters of Mie theory for Pluto's atmosphere:


Enjoy,
Fridger

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Beautiful screenshots that make it even more painful waiting for a release.

Will high resolution textures like this be part of the standard package, or available as a separate download?

Meanwhile, I'll have to watch my own rendering of the Milky Way...

Thanks for the "flowers".. The Milkyway in celestia.Sci is based on Nick Risinger's famous photographic one. I have eliminated all identified stars (with some GIMP tricks) and then replaced them by the 2 million GAIA stars from celestia.Sci that Andrew has prepared. Nick R. has granted me in written form that in the resolution shown his MW results may be used in celestia.Sci. He was not willing though to grant me a higher resolution (which of course exists) .

I am not yet certain about the general texture resolution in the celestia.Sci release and thus I am still experimenting. In any case: all textures that don't forbid it by Copyright will be made available. I have recently experimented with a new 16k VT set all in high-quality DXT format, including .dxtnm (crucial!) for the Normalmaps, all in the same resolution! This set renders ultra-smoothly via the tiles and was prepared with my optimized texture tools and normalmap tools.

If I knew how to make them available in the distribution that would be my choice! 16k can still be handled pretty well in downloads yet is amazingly detailed and smooth already...and unbeatably FAST.

Aha! Where are your MW data from? Looking very interesting.

Actually: I now remember there was another photographic MW atlas available online even in higher resolution. Unfortunately, the software used by the author for digital assembly of the individual photos was by far too inaccurate or even buggy. These data were not usable with our standards, therefore. I hope your nice image above is not related to this atlas? Did you check the Ra-Dec accuracy carefully?

Cheers,
Fridger

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Sounds promising


I have to admit that this was a kind of a joke.
This Milky Way image is the result of stacking 9 photos I've taken in the mountains of Gran Canaria recently. As long as I don't have celestia.Sci to play with, I spend my time with some astro photography.
So I guess, the data should be pretty accurate, but maybe the mapping is not perfect because of lens distortion, and the color rendition might be totally artistic

Nice! Actually that's how our famous MW photographers have most probably also started. In any case, the accuracy requirements during the assembling and aligning stage of thousands of individual shots requires professional level equipment (as Nick wrote to me). And he had to travel all around Earth for completing the job

Anyway, your venture sounds like a most gratifying and creative holiday project!

Cheers,
Fridger

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Gravitational Lensing (GL)

Currently, GL serves as a main tool in the all-important searches of Dark Matter, EXO planets etc. There is practically NO guesswork involved: The underlying framework is Einstein's highly respected General Relativity according to which light rays are deflected by gravity (i.e. Mass).

The nice feature is that in the limit of weak gravity the GL formalism collapses into one that is isomorphic to Optics, with caustics and all that. Hence in practice good knowledge of Optics is sufficient for working out GL phenomena quantitatively. One of my favorite reviews (for physicists though) is by Prof. Ramesh Narayan, Harvard Univ

In celestia.Sci, Dawoon (aka dirkpitt) and I implemented a complete framework of so-called strong, weak and micro lensing. Here is a typical rendering of a deep space configuration for strong GL:

Consider the very massive cluster of elliptical galaxies, notably NGC 6166 in the image center. The first image has Gravitational Lensing effects switched off. Then it looks like so:
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]


Now, let's switch on GL.

Explanation:
========
In this display, the very massive E2 galaxy NGC 6166 is 273 Mpc (!!) away from the observer, while far behind NGC 6166 at ~420 Mpc distance is our "tiny" SBc- type Milkyway, which cannot be observed directly anymore. Milkyway, NGC 6166 and observer are approximately (but not exactly) positioned on a straight line, whence --according to GL--we expect a magnification of the tiny Milkyway into a distorted double image of the SBc-type MilkyWay, looking as follows:
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]


Bringing the MW, ngc 6166 and the observer more precisely into a straight-line configuration results in a conspicuous so-called "Einstein circle", with the super-massive NGC 6166 located in the center. ...Indeed!

See here:
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]


++++++++++++
By carefully measuring the size of the Einstein ring, we can learn something important about the system. what could that be???
++++++++++++

Enjoy,

Cheers,
Fridger

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Wow, this is beautiful. Thanks for coding it.

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Guillermo Abramson
Bariloche, Argentina

If the distances to the "lens" and the object behind it are known, we could calculate the mass of the lens object?
Or maybe it's the other way around and we want to calculate distances?

Very well! The diameter of the Einstein ring is usually measured as dimensionless angular diameter, but that's no big deal.

Fridger

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Here is another Gravitational Lensing scenario around the elliptical galaxy cluster NGC 487x (northern Coma Cluster). NGC 4874 (Coma A) is a supergiant elliptical galaxy, perfectly suited for great lensing phenomenology...

[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]


The 4 red triangles denote the true region where our MilkyWay is located in absense of GL! As usual GL, produces a magnified distorted double image of our galaxy...I guess you spotted the two images of our SBc MilkyWay galaxy without problems.

Also the distance of the two (asymmetrical) MW images tells us something important! Any idea from where we know the huge cluster masses??

Cheers,
Fridger

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t00fri, can you show color capabilities of celestia.Sci?

Let me explain what I mean: if I were to design from scratch the thing, I would associate in a clear way texture values with physical quantities, like reflectivity in well defined channels; for example when using a 3 channels texture I would want to write in some way in the ssc for each channel that it is centred on a certain wavelength with a certain width (maybe even a non-gaussian shape) with a certain scale to convert integer values (not necessarily linear). Then the spectrum of light sources is used to derive the image and a response is applied to get screen RGB values. I would be able to modify the response, e.g. "match the received luminous intensity with a logarithmic scale ranging from here to there, with R as this channel, G as this other etc.".

With this system I could straightforwardly visualize directly non-natural color data, or get natural color on-the-fly (if the available channels are nearby eye channels).

It seems that Celestia does not have a clear physical definition of texture values; instead textures are considered like images to be shown on screen, one hand-tweaks the textures to appear the right way in typical scenarios, but a global coherence is missing. For example one can see in the same frame the Sun (nearby) and the Earth (FOV 500x):


I expect this to be impossible with a "human eye response" in the sense above; either the sun would saturate or the earth vanish.

Disclaimer: I suspect all of this may be cumbersome to implement in real-time, but I remember you said something about color profiles...

Hi catwrings,

thanks for this interesting suggestion of a color scheme in celestia.Sci.

Unfortunately, as to my original plans about well-defined color in DSOs, we are very much behind schedule, since the incorporation of our general Gravitational Lensing framework took far longer than planned...

What I have implemented are three distinct types of color schemes for DSOs.

• vivid DSO colors (Saturation S = 1)
• adaptive DSO colors (Saturation S increases with decreasing distance from observer)
• Grayscale DSOs (Saturation S = 0)

If your are interested, I can easily display some examples.

Moreover (as in Celestia) there are two star color schemes, one vivid (blackbody) and one weak classic.

Your color proposal clearly needs extensive examination and preferably also some experimentation, before its pros and cons can really be evaluated..

For a complicated program like celestia.Sci there are many considerations that need to be taken into account. But I'll certainly continue thinking about your idea. Let's see what will come out of it.

The usual color management uses standardized color profiles that allow a transformation from one device to another one, such that the resulting colors look identical on all used devices. Or, one can e.g. transform a galaxy photo from Hubble to SDSS colors and compare with related SDSS photos..

So far your proposal looks elegant but not obviously practical. Notably when it comes to requirements like retaining compatibility with the huge number of existing add-ons etc. Or what about speed in texture rendering?

Fridger

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Gravitational Lensing cont.

In celestia.Sci we can repeat and confirm Einstein's famous prediction of General Relativity!

Accordingly, a light ray which tangentially grazes the surface of the Sun is deflected by 1.7". Einstein's prediction was confirmed in 1919 when the apparent angular shift of stars close to the limb of the Sun (see Fig.1) was measured during a total solar eclipse (Dyson, Eddington & Davidson 1920).



In celestia.Sci this is much easier : From Earth, we look at the star HIP 38122 close to the solar rim with GL switched off and the four red triangles pointing to the star's center position:

[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]



Now we switch GL on with a simple click on the Workflow (W) toolbutton: Strong Lensing Work . The activation of GL is visible both by the red bar in the tool button menu and the red GL icon to the right of the Time display.

[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]


You may now clearly see a tiny shift of the HIP 38121 star outwards compared to the NO-lensing position still marked by the 4 red triangles!
The deflected distance may be read out to be precisely 1.7 " ...(cf Fig. 1)!!

Enjoy,
Fridger

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Arctic & Antarctic Sea Ice, Land & Water Masks

Most of us have always used the BMNG imaging data for excellent renderings of Earth. Originally from NASA Blue Marble, via the Motherlode, a hires mask for the sea-ice made its way to this site:

http://www.shadedrelief.com/natural3/pages/extra.html

and offers a nice 16k hires sea-ice mask. An excellent Land & Water data file was long ago prepared by joint efforts, notably by cartright (aka Stephen). I have always placed it into the surface texture's alpha channel, which is somewhat economic. One of my F-TexTools (tx2rgba) does the job very fast. In two of the following three screenshots I left the Preferences DockWidget active, showing how easy it is to apply different appropriate simulation times for the Antarctic and Arctic settings.

If you know your GIMP quite well, the installation of the 16k sea-ice mask is a matter of minutes... Here are a few shots of various sea-ice views:

Antarctic:
======
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]


Arctic:
====
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]




Note that via my Nmtools and F-TexTools

viewtopic.php?f=6&t=70

all 16k sized textures are very quickly transformed into high-quality, optimized VirtualTextures in DXT format. The great benefit is that the screen operations with 16k hires resolution perform "lightening fast".

Enjoy,
Fridger

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