Lao Tzu
64 lines
5.5 KiB
HTML
Executable File
64 lines
5.5 KiB
HTML
Executable File
<title>NIGHT SKY</title>
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<body>
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<div id="body">
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<h1>NIGHT SKY GENERATION</h1>
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<p>
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This is just a small program I wrote in Python to generate a starry night sky. It uses Pillow for image processing,
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and it was a fun exercise in basic random image generation. I wanted to make a program that you could run over
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and over and it could always spit out a pretty picture that was completely unique each time. Naturally, the program
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employs a lot of random number generation using NumPy as well as some basic linear math for galaxies. The largest
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challenge is trying to get the stars to look somewhat natural in color and shape, and that's where I think the
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program needs most development. For now however, I think the results are acceptable.
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</p>
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<p>
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I came up with the idea during development of this website. I needed a pretty night sky backround for my homepage,
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but I didn't want to just use some stock image and I don't have any graphic design experience, so I just wrote a
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script for it in Python. I wanted it to look like a night sky if it was unobstructed by the atmosphere and light
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pollution; where the milky way and all the stars are highly visible. I also really wanted to have a program that could
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use random number generation to build a really pretty picture every time without the need for human tweaking, so you
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could just run the code and get a unique and beautiful picture.
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</p>
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<p>
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The first thing I did was get Pillow (an image-processing library for Python) as well as NumPy (a math library) for its
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many random number generators, and I started drawing little yellow circles at random locations with random sizes. This
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made a picture, but not really anything close ot a night sky yet. The real night sky has stars distributed in clusters
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broken by empy space. It also has a big streak of stars and gasses across the night sky where the Milky Way passes through
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our sky. Finally, stars are not just yellow, they're usually closer to blue or white with variation based off of temperature.
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I shelved the coloring issure and went on to create a galaxy system. I wrote a function which takes an x-value,
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a slope, and an intercept, and spits out a y value corresponding to the linear equation defined by those parameters.
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This line will be the center of the galaxy which the stars will cluster around.
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</p>
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<p>
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To actually get the stars clustered around the line, I used a normal distribution random number generator to randomize
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the distance of each star from the center line, with an average distance to make the distribution appear more natural.
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This produces a nice line distribution , but doing this only once leaves the 'galaxy' looking kind of weak. So I draw stars
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around the line multiple times with different normal distributions to produce a layered sort of look, which I think makes it look
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much more natural. Finally, I just kept my initial code to generate stars at random locations to build a background
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behind the galaxy.
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</p>
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<p>
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Next it was time to tackle the coloration. Initially I just tried generating each star with a random RGB value and tried
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restricting the range of the R, G, or B in order to keep the stars within the range of reality (no green or purple stars, etc).
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This didn't really work very well. I realized that stars' colors are determined by their temperature and there is a direct
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correlation between a star's color and temperature in kelvin. So after doing a little research, I found a Python script that
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does just this! It converts degrees kelvin into an RGB value. All I had to do was give each star a random temperature based
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on the range of actual star temperatures, and then I could get rid of all impossible RGB values for stars. This works well, although
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there are still too many red stars which are generally pretty uncommon in the night sky. I think it actually makes the image look
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more interesting from an aesthetic perspective, even if it's not quite accurate.
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</p>
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<p>
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The last thing I've done was add star clusters, in addition to the galaxy system. This one is pretty simple. I just
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pick a random set of points and generate stars at a random distance. It leaves the image looking a lot more realistic
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and beautiful.
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</p>
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<p>
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That is as far as the script goes for now. I have several issues with it I want to improve in the future. One glaring
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issue is that Python is very slow, and generating high-resolution images can take several seconds. I'd like to rewrite
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the program in a more memory-efficient langauge like C++ to reduce processing time. Another issure is that the actual individual stars are pretty
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rudimentary. They're just circles with a blur effect. I'd like to introduce some kind of flare to them to make them more
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interesting. I would also like to include other types of astronomical bodies like comets, nebulae, planets, etc. I think
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the program as it exists is still compelling and I am happy with the images it produces. That's all!
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</p>
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</div>
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</body>
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