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19 May 2024 19:41:21 EDT (-0400)
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From: Thomas de Groot
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 02:59:21
Message: <58a6ad59@news.povray.org>
On 16-2-2017 19:59, Kirk Andrews wrote:
> So, I'm starting to get my head around what's happening with the lakes not
> filling up. As it searches for a point lower than the water level in an
> increasing radius, it doesn't take into account whether or not the water can
> actually flow that way.
>
> So, for example, maybe the lake extends away to the north, beyond the current
> testing radius, and there is a ridge to south, but then a lower point. Since the
> lake extends away to the north, the algorithm detects that as the lowest point
> (equal to the current water level), and therefore does not raise the water
> level, but does keep expanding the radius. Eventually, it does detect a lower
> point, but it's on the other side of the ridge. Right now, the algorithm has no
> method to detect that the water can't get there from here, so it goes ahead and
> jumps the stream through the rock to the other side.
>
>

Ah. That is a complication indeed.

-- 
Thomas


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From: Thomas de Groot
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 03:35:12
Message: <58a6b5c0@news.povray.org>
On 16-2-2017 19:59, Kirk Andrews wrote:
> So, I'm starting to get my head around what's happening with the lakes not
> filling up. As it searches for a point lower than the water level in an
> increasing radius, it doesn't take into account whether or not the water can
> actually flow that way.
>

I used here a height_field where a drainage pattern has been eroded with 
the help of a succession of different applications. As I expected, the 
pattern is not perfect, with ridges barring the drainage courses in 
several places. I have not yet found a single application that does the 
job faultlessly.

However, the code does a good job I think in joining the lowermost areas.

-- 
Thomas


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From: Thomas de Groot
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 07:52:53
Message: <58a6f225@news.povray.org>
In this particular example, the erosional process seems to have been 
better. A pity I cannot reproduce exactly what I did to get there as I 
was just messing around without paying to close attention to the 
different steps.

-- 
Thomas


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From: Kirk Andrews
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 08:30:01
Message: <web.58a6fab0bd8ebaffd61e8dc40@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> In this particular example, the erosional process seems to have been
> better. A pity I cannot reproduce exactly what I did to get there as I
> was just messing around without paying to close attention to the
> different steps.
>
> --
> Thomas

That's looking really good, Thomas!

Which software are you using for erosion? Now that I don't have a PC anymore,
I've got to find something to run on my Mac.


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From: Stephen
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 08:46:12
Message: <58a6fea4$1@news.povray.org>
On 2/17/2017 1:29 PM, Kirk Andrews wrote:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> In this particular example, the erosional process seems to have been
>> better. A pity I cannot reproduce exactly what I did to get there as I
>> was just messing around without paying to close attention to the
>> different steps.
>>
>> --
>> Thomas
>
> That's looking really good, Thomas!
>

It does indeed. :-)

> Which software are you using for erosion? Now that I don't have a PC anymore,
> I've got to find something to run on my Mac.
>

FYI
Thomas is a PC user.

I am trying to replicate it in Blender as a goal in learning to use 
Blender. If I get anywhere I will post it here. But there is a lot to 
learn, an awful lot. :)

-- 

Regards
     Stephen


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From: Kirk Andrews
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 09:00:03
Message: <web.58a700b3bd8ebaffd61e8dc40@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> On 16-2-2017 19:59, Kirk Andrews wrote:
> > So, I'm starting to get my head around what's happening with the lakes not
> > filling up. As it searches for a point lower than the water level in an
> > increasing radius, it doesn't take into account whether or not the water can
> > actually flow that way.
> >
> > So, for example, maybe the lake extends away to the north, beyond the current
> > testing radius, and there is a ridge to south, but then a lower point. Since the
> > lake extends away to the north, the algorithm detects that as the lowest point
> > (equal to the current water level), and therefore does not raise the water
> > level, but does keep expanding the radius. Eventually, it does detect a lower
> > point, but it's on the other side of the ridge. Right now, the algorithm has no
> > method to detect that the water can't get there from here, so it goes ahead and
> > jumps the stream through the rock to the other side.
> >
> >
>
> Ah. That is a complication indeed.
>
> --
> Thomas

To do this *right*, I'm thinking you'd have to do a full-blown physics
simulation. But, I'm wondering if we can't get to a reasonable approximation
with some extra trace checks. Right now, it's only checking straight down from
above, but if we also checked across from the center point, maybe we could
eliminate points that didn't have a straight path from here to there. I
experimented with that idea some but I can't tell if it's really working yet.

https://www.dropbox.com/s/49nmnd5z1kzhms0/Water4.pov?dl=0


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From: Kirk Andrews
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 09:00:04
Message: <web.58a70188bd8ebaffd61e8dc40@news.povray.org>
Stephen <mca### [at] aolcom> wrote:

> > Which software are you using for erosion? Now that I don't have a PC anymore,
> > I've got to find something to run on my Mac.
> >
>
> FYI
> Thomas is a PC user.
>

Oh, I'm sure; but some of them are available on both platforms. I used to use
WorldMachine, but it's PC only.


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From: Bald Eagle
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 10:20:00
Message: <web.58a71383bd8ebaffc437ac910@news.povray.org>
Not sure if this helps any - might be useful as a lead...
Busy at work, but couldn't help peeking

http://ncsu-geoforall-lab.github.io/geospatial-modeling-course/grass/simwe.html

http://www4.ncsu.edu/~hmitaso/gmslab/irwin/irwin1.html

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=simwe+model

http://geoinfo.amu.edu.pl/sgp/LA/LA17/LA17_081-086.pdf

http://tucson.ars.ag.gov/isco/isco10/SustainingTheGlobalFarm/P081-Mitasova.pdf


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From: Kirk Andrews
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 12:10:00
Message: <web.58a72d8cbd8ebaff66e1985f0@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> Not sure if this helps any - might be useful as a lead...
> Busy at work, but couldn't help peeking
>
> http://ncsu-geoforall-lab.github.io/geospatial-modeling-course/grass/simwe.html
>
> http://www4.ncsu.edu/~hmitaso/gmslab/irwin/irwin1.html
>
>
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=simwe+model
>
> http://geoinfo.amu.edu.pl/sgp/LA/LA17/LA17_081-086.pdf
>
> http://tucson.ars.ag.gov/isco/isco10/SustainingTheGlobalFarm/P081-Mitasova.pdf

Oh man, looks like I've got reading to do.


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From: Kirk Andrews
Subject: Re: Tracing the path of streams
Date: 17 Feb 2017 12:10:00
Message: <web.58a72e5fbd8ebaff66e1985f0@news.povray.org>
> To do this *right*, I'm thinking you'd have to do a full-blown physics
> simulation. But, I'm wondering if we can't get to a reasonable approximation
> with some extra trace checks. Right now, it's only checking straight down from
> above, but if we also checked across from the center point, maybe we could
> eliminate points that didn't have a straight path from here to there. I
> experimented with that idea some but I can't tell if it's really working yet.
>

Or, I suppose it could be as simple as what paint programs do with the fill
tool, and treat it more like square pixels.


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