First of all, thank you for this fantastic program!
I miss only two things:
I want to be able to look around just by moving the mouse. The coursor (cross) has to be switched off then, of course. Could you please, please implement that? If you need a code-fragment for a nice, clean, sysetmfriendly way how to do this, I can give you one.
In celestia you can make the stars appear as points instead of fuzzy blobs. And you can "fade" the brightnesses (with the keys [ and ]). This however is a bit tricky. I believe it is done with a technique that is called "exposure function". The formula should look something like this:
grey_value = 255(1-exp(-birghtpow(2.51,(8-mag_vis)))); The variable bright is then in the range of 0.001 to 0.01. You can fade in real-time and the sky looks always realistic (at least to me).
These two features would make the program absolutely perfect in my eyes. And this is supposed to mean something!
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If you set flag_point_star to true in the config file you will get 1 pixel stars and planets.
You can also scale magnitudes with star_mag_scale.
You can change these in the program through the text menu, if you enable that in the config file.
Let us know if these don't do what you are looking for.
AH, very good!
But there are still a few drawbacks:
I want to be able to scroll in finer steps.
As far as I have seen, I can only fade in steps of 1.0 (and I cannot go below 1.0). This is the same problem as with the cursor keys and the zoom keys: on fast computers with frame rates of 180 the steps could be much finer and it would still be real-time. The zoom speed is much too fast on my computer. The steps are much too coarse.
The days of the micro-switch-joysticks are over. When I use the cursor-keys to scroll around I feel like 15 years ago. Today we are looking around with the mouse. For example in all Ego-shooters. But also in non-game-programs. It is not a shame to use mouse-look, it is natural. But in the windows-version it is not implemented as far as I see. This is also the solution for the coarse-step-problem above: with the mouse everyone can scroll in the speed and fineness he or she likes. One could use the mousewheel for zooming.
Finer star-fading is one thing, but there remains an issue. I don't know if you already have adressed it in your program: The star-magnitudes are exponents. A star of ma=1 is 100 times brighter than a star of ma=6. How to display this huge range of brightnesses on a monitor? Setting ma=1 to 200 and ma=6 to 2 gives poor results. It looks not realistic. I know, I'm carrying owls to athens. You surely have thought about that more than I. But have you come to the same solution as I, namely to use the exposure function? Or do you know, how it is done in Celestia, where it looks quite good (with point-stars)? The other solution is of course to use disk-shaped stars, but I mean only point-stars here.
Thank you for your kind support.
I agree we definitely need to implement mouse view (maybe dragging the sky with the mouse cursor)
Sorry but I think star brightness is better managed in stellarium than is celestia (at least as far as I know) and I am personally fully satistfied with it. The problem with the stars rendering is much more complex that only to use an exponential magnitude scale. The real problem is the eye adaptation to luminance. And this is adressed in stellarium with a full eye model (the tone convertor class). Stellarium also use disk-shaped stars to increase the brightness range wich is very limited on a CRT device.
Thank you very much for your reply.
To prevent one error you could make in advance, I give you my philosophy when using Stellarium:
After starting the program, I am on the meadow. It's only the sky, the ground and me. Nothing else. There are no menues. There are no pointers. There are no cursors. There is no text or numbers, anywhere. It looks like in reality. The stars are points. The moon is small. The milky way is very dim (if visible at all).
I want to look around now. My right hand rests on the mouse. The fingers of my left hand rest on a, s, d, f and the space bar. I move the mouse to look around. No buttons or keys are pressed. When I move the mouse to the right, I turn my head to the right. When I move the mouse upwards, I turn my head upwards. I am not in an airplane. I am standing on a meadow. The wind is blowing slightly into my face. It is warm. It smells good. I am not using a technical device to look around. I just turn my head - by using the mouse. When I drag the mouse towards me, I look towards me, on the ground.
Now I want to learn the constellations and thier names. I can switch them on and off by using the keys c and v. I don't have to look on the keyboard for that, because I know v is the key below f and c is the key below c. I can keep looking at the stars while switching the lines and names. This is great. A great program. It is done as real and as comfortable as possible. The programmer is a real human being. He feels and thinks like I do.
On many evenings I have learned to recognise the constellations. Now I want to know more. What is the name of this star. I want to be able to point to a single star. I look at it and press the left mouse button. A faint circle is drawn around the star in the middle of the screen. But I didn't mean that star! I meant the star to the left of it. So I'm moving the mouse a bit to left (sorry - I'm looking a bit more to the left) and the correct star is highlighted and the information is shown. I press the left mouse button again and the marker-circle is gone. I did not have to hold the mouse button, because then my finger would probably have become stiff or broken or numb. It all has to be very relaxed. No stress while looking at stars, please!
I am standing on the meadow. Above me the sky full of stars. It smells like a beautiful summer night. And I am learning the constellations. With Stellarium.
I believe you have recognised the error you could make. PLEASE not.
The mouse-move- and mouse-scroll-sensitivities have to be adjustable of course.
To simulate the human eye is the noblest thing you can do of course. And it looks great when I look into the sun. But I doubt a little if it works for stars as well. Especially for point stars. But even for disk-stars I get fancy effects. If I look at Ursa Major for example and zoom in on it, the relative brightnesses of the brightest stars change. This comes probably from the eye-adaption. But it looks unrealistic! You get a good page on the exposure function when you search for it in google (a page of a hugo elias). Maybe this page can convince you to implement it at least as a feature.
Thanks for your pleasant reply :)
The problem with your idea is that you want to be able to control your head movement AND to select objects with the mouse in the same time (the pointed star is the one at the ceter of the screen). The problem is that most of the time, when you want to select an object you don't want the point of view to change.
The best solution is I think to drag and drop the sky. Need to be implemented.
Now for the stars brightness, the eye adaptation works fine as long as you don't zoom in. Because when you zoom in, you don't use your eye anymore. What should be simulated is something like the eyes seeing thru a device like a telescope. But at each different zoom power the device must change its characteristics so that it looks intuitive to users (and beleive me it is not trivial)..
It would be nice to have a SEARCH function to quickly find an object - above or below the horizon and the capability to SAVE the current sky positions for reloading, rather than having the program load the same S(outh) cardinal point each time. I feel foolish to have spent a couple of hundred $ on other less capable and less realistic programs before finding Stellarium. If you added some additional features (mouse controls, more photos, web based updates of new objects, etc.), I'd gladly pay for this program as "shareware".
Cite: "The problem is that most of the time, when you want to select an object you don't want the point of view to change."
You are completely right!
Discussing such things is so much fun and really helps to make them better. Ok, here I come up with my next suggestion:
Head movement as I described: No visible pointer/cursor. Natural directions. No airplaine, NO DRAGGING around of the sky! I sometimes can't even drag around my 2,5 year old daughter, because she is so heavy. How should I be able to drag around the whole sky then? (-> Immersion gone.)
But now for the selection: left clicking results in appearance of a pointer/cursor. Now mouse-moving moves the cursor and the sky i.e. head is still. Very relaxed you can click on stars now. Left click again and the cursor is gone and I can look around again.
What do you say to this solution?
Zooming: with mousewheel, please. Sensitivity adjustable. UP = Zoom in, DOWN = Zoom out.
I definitely agree, that simulating the human eye is not trivial. But what I suggest with the exposure function is not so trivial either. And it look really good, believe me, especially for point stars. I could send you an example program of mine. And you can adjust it manually, to fit your psychological needs. Maybe starlight is so intricate and delicate, that there are even psychological effects. A starry sky that looks real for somebody maybe doesn't for somebody else. Everyone has a different monitor. But with the exposure function and manual adjustment in real-time everybody could make the brightnesses fit his or her needs.
PS: Of course switching the selection mode with the left mousebutton and selecting with it at the same time is impossible. But we have still the right mousebutton. So we could switch between the two modes with the right mousebutton and do the selection with the left exactly as it is already done.
There are many astronomy-programs available. But Stellarium stands out. Why? What makes Stellarium special? Well of course its realism.
When you can use a computer program or a simulation and can feel like really being there this is called immersion. Many think this has only to do with graphics. The more real the graphics, the higher the immersion. But this is only half of the truth. Immersion has to do with as many human senses as possible. So there is e.g. also the question: is the sound real? But what most people forget: immersion can be destroyed, when the usage of the keyboard or the mouse is not adequate.
Take e.g. the two possibilities to look around in Stellarium: 1. moving the head 2. dragging the sky. Which one is more "immersive"? Number 1 of course.
Or take the keyboard: 1. constellations are switched with CTRL-ALT-P and SHIFT-q or 2. with c,v. If it were 1 one would always have to take ones look off the screen. Immersion would be destroyed.
Immersion is also a question of keyboard- and mouse- handling. And immersion is easily destroyed by seemingly small details.
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