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After seeing Cassini's recent pictures of some of the icy crater fields of
Saturn's moons Dione & Tethys, I was inspired to dig up my old crater
height field generator I wrote on the Amiga to see how it works on Linux.
As you can see from the quick test below, it functions ok (yes, the texture
looks more like plastic than ice :). I've just improved the way each crater
is blended into the existing landscape, although I'm still not completely
happy with the crater generation algorithm.
To be perfectly honest, I can't remember the algebra behind some of the
parameters. That's what happens when you don't use enough comments & other
documentation and you then try to decipher 5 year old code. :) I'll just
have to sit down & reverse-engineer the geometry...
The crater generator height field output is only 8 bit .pgm, but I'm
thinking of adding 16 bit & maybe even simple floating point (hdr) output.
If anyone's interested in this crater generator, I'll post the C source &
Linux binary (in the appropriate area).
PS. The crater heightfield is tileable.
Post a reply to this message
Attachments:
Download 'planetg2s.jpg' (203 KB)
Preview of image 'planetg2s.jpg'
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High!
PM 2Ring wrote:
> As you can see from the quick test below, it functions ok (yes, the texture
> looks more like plastic than ice :). I've just improved the way each crater
> is blended into the existing landscape, although I'm still not completely
> happy with the crater generation algorithm.
The "blending into the existing landscape" is solved well - younger
craters obliterate older ones instead of simply adding up their
elevation values (like in John Beale's HF-Lab)... but the outer wall
slopes of craters are too steep!
> If anyone's interested in this crater generator, I'll post the C source &
> Linux binary (in the appropriate area).
Oh yes, that would be nice... although I'm mostly occupied with my
preparations for starting PoVEarth, I sometimes find the time for some
doodling in between, and creating cratered moons/asteroids would be
relaxing!
See you in Khyberspace!
Yadgar
>
> PS. The crater heightfield is tileable.
>
>
>
> ------------------------------------------------------------------------
>
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"PM 2Ring" <nomail@nomail> wrote:
> After seeing Cassini's recent pictures of some of the icy crater fields of
> Saturn's moons Dione & Tethys, I was inspired to dig up my old crater
> height field generator I wrote on the Amiga to see how it works on Linux.
I think my eyes and brain are playing tricks on me.
Probably just a result of the lighting...
but the craters look kind of dome-like. Which gave me an
idea!! I took the image, stuck it into Photoshop, and inverted it (whites
to blacks and blacks to whites.) I couldn't resist; hope you don't mind!
Ah, the evils of post-processing! :-)
Here's the result...
Post a reply to this message
Attachments:
Download 'planet_altered.jpg' (107 KB)
Preview of image 'planet_altered.jpg'
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Kenneth wrote:
> I think my eyes and brain are playing tricks on me.
> Probably just a result of the lighting...
> but the craters look kind of dome-like.
Whoah .. I was the same! I even went to the casini website and took a
look at the source material, sure enough, some of *theirs* look domed too.
But I was convinced they wouldn't be, so I went back to the pov and
looked again, but no matter what I did, they were still domes.
Then your post came in and the inversion clearly shows they are concave
rather than convex. So I opened the original again to see if I could see
what went wrong. Still domes.
So I gave up and started looking at the detail .. and all of a sudden I
noticed they were concave! Now I can't see them as convex any more!
Stupid eyes!
Cheers!
Rick Measham
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Rick Measham <rickm*at%isite.net.au> wrote:
> Whoah .. I was the same! I even went to the casini website and took a
> look at the source material, sure enough, some of *theirs* look domed too.
Hi all,
the dome effect is influenced also very much by the direction of the light.
In the image you see twice the same foto of a moon crater.
The right one is just upside down.
Funny, he?
Yours,
Bu.
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Attachments:
Download 'comparison.jpg' (57 KB)
Preview of image 'comparison.jpg'
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"Burki" <nomail@nomail> wrote:
> Rick Measham <rickm*at%isite.net.au> wrote:
> > Whoah .. I was the same! I even went to the casini website and took a
> > look at the source material, sure enough, some of *theirs* look domed too.
>
>
> Hi all,
>
> the dome effect is influenced also very much by the direction of the light.
>
> In the image you see twice the same foto of a moon crater.
> The right one is just upside down.
> Funny, he?
>
>
> Yours,
> Bu.
AFAIK this effect is caused by our brains as they expect the light coming
from above. i find the attached example very impressive. in that case it is
the opposite effect. a dome-shaped surface looking like a hole.
just my 2 cents ;-)
Roman
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Attachments:
Download 'compare2.jpg' (49 KB)
Preview of image 'compare2.jpg'
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High!
> the opposite effect. a dome-shaped surface looking like a hole.
Ayers Rock, isn't it? But I wonder that there's a broad path to the top...
See you in Khyberspace!
Yadgar
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"Roman Reiner" <lim### [at] gmx de> wrote:
> AFAIK this effect is caused by our brains as they expect the light coming
> from above. i find the attached example very impressive. in that case it is
> the opposite effect. a dome-shaped surface looking like a hole.
A concept also explored by our favourite graphic illusionist Maurits Escher,
in his print "Concave and Convex", i.e.
http://www.worldofescher.com/gallery/jpgs/P9L.jpg
Simple, but cool!
Bill
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Hi all,
Sure it's the brain. Isn't it always ?
And the Uluru thing is much more impressive.
Yours,
Bu.
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"Kenneth" <kdw### [at] earthlinknet> wrote:
> "PM 2Ring" <nomail@nomail> wrote:
> > After seeing Cassini's recent pictures of some of the icy crater fields of
> > Saturn's moons Dione & Tethys, I was inspired to dig up my old crater
> > height field generator I wrote on the Amiga to see how it works on Linux.
>
> I think my eyes and brain are playing tricks on me.
> Probably just a result of the lighting...
> but the craters look kind of dome-like.
I know what you mean. :)
> Which gave me an
> idea!! I took the image, stuck it into Photoshop, and inverted it (whites
> to blacks and blacks to whites.) I couldn't resist; hope you don't mind!
> Ah, the evils of post-processing! :-)
>
> Here's the result...
I like it! I'll try to post the craterfield generator tonight. I just need
to write some docs for it...
Post a reply to this message
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