Lights From Space Map Help

[BriniaSona]

I am trying to make a night map from space - http://svs.gsfc.nasa.gov/vis/a030000..._composite.png

I want to mimic that look.

I tried using a brush that made spread out pixels and dots, but it's pattern is always the same. Is there anyway to make the patter it makes random (CS6). Or is there a brush I can download for this?

The attatched image shows the problem with the uniform patterned brush. It just doesnt look natural.

What is the best course to go about for making night cities?
Untitled.png

[Chick]

Hi Brinia. In Photoshop, you have a lot of control over your brush, so check it out this way....

Start by opening a new image window, then select your brush tool to a medium sized round. Now open the Brushes panel and click on Brush Tip Shape. That allows you to change things like Roundness and Spacing. Then check the Shape Dynamics and click on it to open that menu. That allows you to set the Size, Angle, and Roundness "Jitter" or random changes. Continue to check out Scattering, then Color Dynamics and Other Dynamics, etc, until you see how each one affects the brush.

Once you are familiar with these ways to adjust or randomize what your brush does, you should be able to get the effects you want.

[Azélor]

Personally, like I did on a starfield map, I would recommend using simple white dots placed randomly. Photoshop have options to randomize the point placement in the brushes options.
Lower the opacity of the layer and you should be set.
Large cities also tend to have a glow effect around them.

[BriniaSona]

This is my latest attempt. Maybe I can try adding a minor glow to areas.

tmp_8628-Screenshot_2015-11-28-11-51-58105522022.png

[Durakken]

#1 figure out your city shape and size.
#2 figure out the lighting level of area... For example, a peasant is only going to use a fire lit around their hut maybe while the center of the city might have giant bonfire that is lit every night. Modern Cities are generally going to have lights along their roads with downtown areas being lit up by bilboards. The more active night areas are going to have more light and thus the overall brightness is going to be higher than as you travel out ward. Roads themselves depending on the era may be lit or may not be lit.
#3 Every 30 to 50 kilometers there will be at least a little light along the road because there should be small town of some sort there. Major cities are going to obviously be very bright as there is more light while hamlets, villages, suburbia will be less bright in the overall depending on the era.

Now... to make it look natural what you need is the understanding that light is radial usually. It's brightness and size is largely determined by distance. It follows the ... i think its called the square law. Basically that means, let's say you have a light that fills an area of 10x10 cells with 100 lumens (light units) at 10 feet... So each cell has 1 Lumen at 10 feet. Now if you step back to 20 feet the grid exapnds to 20x20 but still has 100 lumens in it which means that each cell has .25 lumens in them. In other words, the brightness is divided between all the cells and there are 4 times the number of cell because you doubled the distance resulting in a quarter of the brightness.

Now let's say there are 2 light sources 30 feet a way from each other and you are in the middle of them. Step back so that you are 10 feet from both and you have same result for both above... step back to 40 feet and what happens is that you are now at a point with the 2 light sources overlap. This results in 75x40 grid. Most of the cells will have .125 in them, but in the center 5 columns you have cells with .25 lumen in them. So you have a brighter spot than what it looks like there should be.

So how does this help? Well consider that all this leads us to produce the question... How many lumens are in the area. That depends on how many light grids in the area are overlapping each other. With each new light overlapping a given area the particular area should get brighter. This can be accomplished multiple ways I'd think. 1 way might be to have a brush that goes on lightly, but every time you go over it increases how much gets laid down. Another way is to create layers that have transparency and then have different layers for outer city moving towards the downtown inner city... Another way that I think would be much cooler but probably harder and more tedious is to lay out lights in the city where they would be with different layers representing different types of lights and then us a layer style to give an outer glow that you can adjust allowing you to adjust the height of the map without having to redo where all the lights are.

Hope that lecture on how light spreads helps ^.^

[johnvanvliet]

a few years back i used the "viirs" data to make a full earth map
http://npp.gsfc.nasa.gov/viirs.html

65535 x 32768 pixels
i have many images posted on a different site
http://forum.celestialmatters.org/viewtopic.php?f=9&t=606
http://forum.celestialmatters.org/viewtopic.php?f=9&t=451

the 4 32768x16384 px images are in post #2
http://forum.celestialmatters.org/vi...9&t=606#p11722

and youtube videos
https://youtu.be/-kYH2kUuiVQ
and
https://youtu.be/ArOI4QCLMXA




the resources i used to colorize the 32 bit floating point data ( the raw data is 32 bit float )
is the ISS archive
http://eol.jsc.nasa.gov/

images like these
http://earthobservatory.nasa.gov/Fea...CitiesAtNight/
http://eol.jsc.nasa.gov/SearchPhotos...=E&frame=27586
http://eol.jsc.nasa.gov/SearchPhotos...=E&frame=16525
using the photos from different city's to colorize the B&W data
-- took about 3 months

gimp has a colorizing tool ( it creates a gradient from a image -- it is a BUILT IN FUNCTION , NO!!! plugin needed)
then a LOT of air brushing a 64K ( 65535 x 32768 pixels) map is a bit big .
then use the astronaut image to collect the airbrush color , then paint some of the lights with that color and move on to the next color


as "Durakken" put it above

city centers have more people and hence MORE lights in the SAME area
also FREEWAYS and major roads have street lights
these are visible from orbit

and Ports!!!!! boy are those WELL LIT !

[Durakken]

If you need some help with scale and how visible a given light source is... Consider this article http://www.livescience.com/33895-human-eye.html

Now if you say you can see a candle up to 50 km away then you can create a measurement of for every meter that you move away from a candle the will get 0.02 % dimmer (I don't want to figure how to transfer that into the inverse square law). So if you are at a height of 50 km you can resolve 1 point of light for each candle. However if you add another candle you'll be able to see light there at something like 100 km away, but not resolve that there are 2 candles. So if you want to see a light from say, 1000km up you're going to need a lot more candles or the equivalent of it. My math is surely wrong here but that article and this idea should be able to help you tell if something should be seen from the vantage point you're looking at or not.

[Hai-Etlik]

If you need some help with scale and how visible a given light source is... Consider this article http://www.livescience.com/33895-human-eye.html

Now if you say you can see a candle up to 50 km away then you can create a measurement of for every meter that you move away from a candle the will get 0.02 % dimmer (I don't want to figure how to transfer that into the inverse square law). So if you are at a height of 50 km you can resolve 1 point of light for each candle. However if you add another candle you'll be able to see light there at something like 100 km away, but not resolve that there are 2 candles. So if you want to see a light from say, 1000km up you're going to need a lot more candles or the equivalent of it. My math is surely wrong here but that article and this idea should be able to help you tell if something should be seen from the vantage point you're looking at or not.

Please stop. Taking real numbers and applying arbitrary arithmetic to them gives arbitrary and meaningless answers. You'd be no worse of just picking numbers at random as your result. It's less effort and more honest (the numbers are meaningless, but it's clearer that they are meaningless) In fact if you just guessed, you'd at least have a chance of being right. Using a linear extrapolation of a quadratic function, it's certain that you will be way, way, way off. If a light is visible at 50 km, then a light visible at 1000 km wouldn't need to be 20 times brighter, it would need to be 400 times brighter.

[johnvanvliet]

if you want a real world comparison

this image is calibrated to the 2006 radiance calibrated earth lights produced by NOAA
-- it is quite dim
-- and a 8 bit screenshot of the 32bit floating point data


the lights as seen from space are quite dim in reality

movies and long exposures in cameras make them look rather bright

also things like the burn off flares on NG fracking wells are VISIBLE
-- the Dakotas ( to the left of center ) and Minneapolis to the lower right - big city



light falls off using a inverse square

1 unite of light at a distance of 1 unit would be 1
BUT
if that 1 unit of light is 2X farther away it will be 1/4 the brightness
4X farther away then 1/16th the brightness

[Durakken]

Please stop. Taking real numbers and applying arbitrary arithmetic to them gives arbitrary and meaningless answers. You'd be no worse of just picking numbers at random as your result. It's less effort and more honest (the numbers are meaningless, but it's clearer that they are meaningless) In fact if you just guessed, you'd at least have a chance of being right. Using a linear extrapolation of a quadratic function, it's certain that you will be way, way, way off. If a light is visible at 50 km, then a light visible at 1000 km wouldn't need to be 20 times brighter, it would need to be 400 times brighter.

Getting these numbers give you an understanding of how much light needs to be there to be seen from space. It's obvious I know that it can't possibly be 20 times brighter and make it clear that to get the right answer you're going to have figure out that thing that I didn't care to figure out and get an answer. I can only guess that you give the answer, because you were too busy complaining than helping and saying whether what you said is a random guess or the actual answer you came to.

Anyways, if the answer is 400 times brighter then you know that what you need to be seen from space is between a light 400 time brighter than a single candle to hundreds of tiny light sources that are overlapping each other. Knowing that small towns in the past reached only around 500 people. villages maybe 2000, average cities were around 1km and had about 20,000 people and larger cities up to 200,000 (ignoring greek city states with 500k to 1m) then you could map that knowing a rough population easily because 1km = 1px = 1town = 1px of barely visible light... villages would have 4 px of barely visible light... and average cities would have 50px to 500px of barely visible light getting brighter towards the center. At least as a general guide, because it's obvious that not everyone is running around with candles and there are flames that are brighter that are used all the time. But then in a modern city it also gives you a rough estimate because street lights and people leaving their house lights on.