Cratered Moon WIP

[HBrown]

One of my (too many) projects is to make a map of a semi-terraformed moon for a friend's science-fiction story. A moon, not the Moon. The project requires craters, and lots of them. Naively, I could just draw a bunch of circles. But I want to draw this in a square grid projection (Platte Carree) because that's easiest to convert into any projection I want later. The more poleward you go, the more distorted the circle becomes. I played around with manual methods, but it was going to take forever.

In the end, I wrote a program which will generate any number of craters across a wide range of sizes and do all the math to fit them into the square projection. I found a Gimp utility that will import paths from a CSV file, so my program generates a matching CSV. When imported, you have a whole lot of new paths - one for each new crater, except for those that cross the 180 degree boundary. Those get two new paths.

I took it for a trial run today, and here's what I got:

I only ran it with 100 craters, and my rendering skills need work, but I'm reasonably pleased with it. The two polar views show that the craters really are round, in spite of how squished they appear in the rectangular view.

Would there be any interest here for this program, once I get the bugs out? It's a command-line program that runs under Windoze, and the CSV only works for Gimp. If there's a similar CSV import facility for other graphics programs, I could easily add a different output as an option.

Thanks for any thoughts, on either the map or the program.

--Hugh

[Ascension]

I like it, has some promise.

[johnvanvliet]

this has been one of the stumbling blocks
this is what i do

for a LARGE moon like ours , it is a fractal nature
BIG ones with smaller ones on top all the way down to the very microscopic

for that i would use masks
a few big crater masks
and many many small crater masks


for that i use a java program ( an old one called PlenetGenisis1.9 )
it is node based

mix a "biased woraly " with a "perlin noise " and add a "craterize" node to it
-- 8bit jpg of the 32 bit floating point


this can then in photoshop or Cinepaint be converted into a "Multiplication mask"
-- normalized to 0 to 1 ! ---


using many of these one on top of the other you can build up a very cratered moon

you can end up with a heightmap
something like this


this is ONLY ONE mask many would be wanted

[HBrown]

That looks a lot easier than the method I was using, and I like the results. I'll have to see if I can find that program.

[HBrown]

I found planetGenesis, but it's far from obvious how to use it. When I open it I get a screen like this:



I can drag the circle in the middle around, but beyond that I can't figure out what I can do with it. The help file is far from helpful, and the on-line instructions seem to be about installation. Clearly, I'm missing something.

Thanks,
Hugh

[HBrown]

Never mind. I found other instructions that tell me how to access the assorted functions.

Thanks.

[johnvanvliet]

in that example i used a FMB noise from "Wilbur"
outputed a 32 bit BT ( converted to tiff )
and the mask ( normalized to 0 to 1 )

notice there is a bit of a ring around the dark circles ( the rim )
the example above was a real QUICK one there is a bit of a dark ring that would need to be removed

in the "layers" of Cinepaint ( a old editor based on Gimp 1 ) and multiplied the layers

not sure if photoshop imports 32 bit floating point images ( i do not use it )

if you want here are two .pG files ( the saved settings from planet genesis )
but the output still needs work to be used as a mask
"test.zip" on my G-drive
https://drive.google.com/file/d/0B6Z...ew?usp=sharing

one is bigger craters the other is smaller ones

[HBrown]

I did some playing around with planetGenesis until i got some stuff that looked reasonable. I created a bunch of maps, based as you suggested on 'biased worley added to perlin 3D noise. I varied the size of the cells in the worley, and once I found a perlin noise setting I liked, I stuck with it. I randomized both the worley and the noise between each map generation.

When I had twenty or so of them I imported them all as layers into Gimp. Gimp is eight bit, so I had to do some fiddling to figure out how to combine the layers so it wouldn't all go to either white or black. In the end, I set the opacity of each to ten to fifteen percent, and added them all on top of a black layer. I then stuck it into the same renderer that I used for my initial stuff at the top of this post. Apples to apples, yes?

This is what I got:


And here's a polar view:


If I spend more time experimenting, I'll come up with better results.

It seems to me that this is a great way to generate the background crater-ness of a small world. When I look at photos of small worlds in our Solar System, I see that many have large craters as dominant features. I don't see how I'd generate these features using planetGenesis, but maybe if I experiment more I'll figure it out.

Also, when I look at the polar view, I see some definite latitude-based biases (they look like concentric rings in the polar view). This is possibly an artefact of how I'm using planetGenesis. At this point I don't have enough experience and data to make that judgment. It's not a serious flaw in any case.

I'm thinking now that I'll use planetGenesis to generate the background and my crater generator program to make some larger craters to plop on top of it to get the bigger features. That's assuming I can get my crater generator to do a few more tricks.

Thanks for pointing out planetGenesis. It's a great tool. Now I just need to learn how to use it...

--Hugh

[HBrown]

Oh, and for completeness, here is the sample you provided, put into the same renderer. Yours is much better:


And the polar view:


Thanks again for pointing out this tool! It's obvious from comparing my initial try with yours I have much to learn.

--Hugh

[johnvanvliet]

on HeightMaps i use 32 bit floating point images
gimp is only 8 bit data for now ( gimp3.0 should handle 16 and 32 bit images )

that way if i make a normal map for 3d rendering or a rendered "shaded" map it is not "stepped" / terraced

there is also something called practice

i have been doing this for a while and trying to get something that dose look like REAL data from real spacecraft


keep at it and things will improve