Among other things, Warp saw fit to write:

>    No matter how long I look at it, I see bubbles, not craters.

No matter how long I look at it, I see craters, not bubbles. ;)

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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Jellby wrote:
> Among other things, Warp saw fit to write:
> 
>>    No matter how long I look at it, I see bubbles, not craters.
> 
> No matter how long I look at it, I see craters, not bubbles. ;)

   Deducing from your smiley I assume it's not true.

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Among other things, Warp saw fit to write:

>>>    No matter how long I look at it, I see bubbles, not craters.
>> 
>> No matter how long I look at it, I see craters, not bubbles. ;)
> 
>    Deducing from your smiley I assume it's not true.

No, it's true, even though the light comes from below, I have no problem
seeing craters and I just can't get my brain to "see" bubbles.

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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Jellby wrote:
> No, it's true, even though the light comes from below, I have no problem
> seeing craters and I just can't get my brain to "see" bubbles.

   It's just so strange. Even when I make great efforts to force my
brain to see craters instead of bubbles, I can't. I concentrate on
one of the circles, visualize the light coming from below (and a
bit from the left), adamantly think "ok, starting from below the
circle, the terrain goes *up* and gets more lighted, then there's
a sharp edge after which the terrain goes *down* as is thus darker,
after which there's a large depression in the ground, after which
the terrain goes again *up*, there's a sharp edge and goes *down*
again", it doesn't help. My brain still sees the exact opposite:
A bubble with its borders dug into the ground. No matter how hard
I try, I cannot get my brain to see a crater. Strange.

   I wonder what would happen if the image was re-rendered with the
light coming from the opposite side.

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I tried once again, this time occluding parts of the crater I was
concentrating on, suddenly my brain flipped the image and now I see
craters instead of bubbles!
   Ironically, now that I see craters I'm unable to see the bubbles...

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Jellby <me### [at] privacynet> wrote:
> Among other things, Warp saw fit to write:
>
> >>>    No matter how long I look at it, I see bubbles, not craters.
> >>
> >> No matter how long I look at it, I see craters, not bubbles. ;)
> >
> >    Deducing from your smiley I assume it's not true.
>
> No, it's true, even though the light comes from below, I have no problem
> seeing craters and I just can't get my brain to "see" bubbles.

Just flip it... craters will turn into bubbles.. or bubbles will turn into
craters.  Same thing happens when I see bubbles--I mean craters on the
moon.

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"Mike Sobers" <sob### [at] mindspringcom> wrote:
> I compiled the crater field generator code by PM 2Ring with a few
> modifications:

Thanks, Mike. To be truthful, the original crater code is by John Walker of
Autodesk (& Fourmilab) and Rudy Rucker developed the random distribution
algorithm. I just fixed it up a little bit & made it output as a
heightfield.

> New functionality:
>
> 1) If desired, large craters can now have a central peak.

Excellent! FWIW, the main crater code conserves volume, although this is
disturbed a bit by the code that 'blends' the outer wall onto the existing
ground. The program assumes that the volume of the impacting meteor is
negliglible, so I suppose it's also ok to ignore the extra volume of the
central peak.

> 2) You can specify erosion - the program will average the pixels the
> specified
> number of times to simulate eroded craters.

That's very handy for places like Mars.

> 3) Output is to .bmp instead of PGM.  Unfortunately, in this current version
> it's a 24-bit file with only 8 bits of info, so an 8000 x 8000 crater field
> produces an output file somewhere around 187 MB.  But you can always
> convert to .png after you make the .bmp output file.  Maybe I'll eventually
> re-write this to produce 16-bit output (.pgm, .tga, or .png).

I stuck with PGM because many NetPBM programs can process data in a
pipeline, reading line by line, so you can avoid writing huge files to
disk. BMP isn't so good for POV since it can only be read & written by the
Windows version, IIRC.

Funny, I was just thinking about fixing it do 16 bit on the weekend...

> Also, maybe I'll create an option to import an existing hightfield.  That
> would allow you to use a pregenerated landscape and then subject it to a
> meteor storm.  Thoughts?

Sounds good to me, and it shouldn't be too hard to implement.

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"PM 2Ring" <nomail@nomail> wrote:
> "Mike Sobers" <sob### [at] mindspringcom> wrote:
> > I compiled the crater field generator code by PM 2Ring with a few
> > modifications:
>
> Thanks, Mike. To be truthful, the original crater code is by John Walker of
> Autodesk (& Fourmilab) and Rudy Rucker developed the random distribution
> algorithm. I just fixed it up a little bit & made it output as a
> heightfield.
>

> I stuck with PGM because many NetPBM programs can process data in a
> pipeline, reading line by line, so you can avoid writing huge files to
> disk. BMP isn't so good for POV since it can only be read & written by the
> Windows version, IIRC.
>
> Funny, I was just thinking about fixing it do 16 bit on the weekend...
>
> > Also, maybe I'll create an option to import an existing hightfield.  That
> > would allow you to use a pregenerated landscape and then subject it to a
> > meteor storm.  Thoughts?
>
> Sounds good to me, and it shouldn't be too hard to implement.

If you want, I can post a link to the source files, and hand the project
back over to you. I don't think I'll have time to work on them much in the
near future.  The only reason I went to BMP is because I am using Windows,
and I wanted immediate feedback on the look of the craterfield.  Also, the
random number generator didn't work when I compiled it under Microsoft
Visual Studio (something about the syntax on the bit shift commands) so it
only produced 1 crater at X,Y = 0,0.  Other than that, it would probably be
better to have a PGM output, especially since that could get you to 16 bit.
I was going to include .jpg and .png output options, but I didn't want to
have to wade through the class definitions to pick out the small bit of
code I wanted.  As it stands, the executible is only 183k and I wanted to
keep it small.  Besides, the complied version I made will probably only run
under Windows anyway.

Mike

PS - same scene, different lighting

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Attachments:
Download 'mars_craters2.jpg' (48 KB)

Preview of image 'mars_craters2.jpg'

Mike Sobers wrote:

>>
> Mike
> 
> PS - same scene, different lighting

Looks nice but, yes there is one :) , it looks to me that the bottom of some
craters is actually higher then the surrounding surface. That way it looks
to me that the crater is added onto the land and not smashed into it.

See attachment


-- 
Ger

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Attachments:
Download 'mars_craters2_high_craters.jpg' (47 KB)

Preview of image 'mars_craters2_high_craters.jpg'

Among other things, EagleSun saw fit to write:

>> No, it's true, even though the light comes from below, I have no problem
>> seeing craters and I just can't get my brain to "see" bubbles.
> 
> Just flip it... craters will turn into bubbles.. or bubbles will turn into
> craters.  Same thing happens when I see bubbles--I mean craters on the
> moon.

Not really... the perspective makes it unreal when flipped, and I see
craters anyway :D

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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