POV-Ray : Newsgroups : povray.tools.general : Finding and extracting GDAL elevation data Server Time: 21 Jul 2019 00:53:13 GMT
  Finding and extracting GDAL elevation data (Message 1 to 4 of 4)  
From: Bald Eagle
Subject: Finding and extracting GDAL elevation data
Date: 12 May 2019 16:45:00
Message: <web.5cd84d809bc00ee54eec112d0@news.povray.org>
I came across this during a search for an entirely different subject (as usual)
but have a long-standing interest in data-based heightfields for rendering IRL
terrain in POV-Ray.

https://wiki.openstreetmap.org/wiki/User:Maxbe/Relief_mit_POVray

In English:
https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fwiki.openstreetmap.org%2Fwiki%2FUser%3AMaxbe%2FRel
ief_mit_POVray

I'm not sure how to locate the grid that I want, and get the data.
I've managed to get that data in the past, and somehow magically open the files
and process them, but it seems to work differently every time, and the last time
I tried I failed.   :(

I'd prefer to do this in Linux, but even if I need Win, I'd just like to get the
data and quickly and efficiently make a heightfield.

A simple, documented workflow would likely help anyone else interested in doing
this in the future.

Like GrADS, the learning curve seems to initially be a bit steep.  :|


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From: Bald Eagle
Subject: Re: Finding and extracting GDAL elevation data
Date: 19 May 2019 01:25:00
Message: <web.5ce0af76356eaf334eec112d0@news.povray.org>
I've found a pretty convenient tool for getting heightfield elevation maps
directly.

https://www.youtube.com/watch?v=Qd2dqe3v7nU

https://tangrams.github.io/heightmapper

Now I just need to figure out a way to make the heightfield, the satellite
image, and the street map align and be scaled properly.


I also have "holes" in my heightfield when I try to texture it with an image
map.  They appear to be at places that are over a certain elevation.   Does that
ever happen?   CAN it ever happen?  I'd expect an image to be rgb in the range
of 0-1.
Is there a mechanism in POV-Ray to scale the rgb range of a heightfield image to
the proper range?


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From: Thomas de Groot
Subject: Re: Finding and extracting GDAL elevation data
Date: 19 May 2019 06:46:23
Message: <5ce0fbbf@news.povray.org>
On 19-5-2019 3:20, Bald Eagle wrote:
> 
> I've found a pretty convenient tool for getting heightfield elevation maps
> directly.
> 
> https://www.youtube.com/watch?v=Qd2dqe3v7nU
> 
> https://tangrams.github.io/heightmapper
> 
> Now I just need to figure out a way to make the heightfield, the satellite
> image, and the street map align and be scaled properly.
> 
> 
> I also have "holes" in my heightfield when I try to texture it with an image
> map.  They appear to be at places that are over a certain elevation.   Does that
> ever happen?   CAN it ever happen?  I'd expect an image to be rgb in the range
> of 0-1.

My intuitive answer to 'Does that ever happen' would be an emphatic 
"No". However... I am no fan of Sketchup and thus do not know what kind 
of quaint things may happen.

> Is there a mechanism in POV-Ray to scale the rgb range of a heightfield image to
> the proper range?

Imo, by putting the image_map-containing texture /before/ any scaling of 
the height_field; but you certainly know that already.

-- 
Thomas


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From: Bald Eagle
Subject: Re: Finding and extracting GDAL elevation data
Date: 21 May 2019 01:50:01
Message: <web.5ce35856356eaf334eec112d0@news.povray.org>
> > I also have "holes" in my heightfield when I try to texture it with an image
> > map.  They appear to be at places that are over a certain elevation.

Simple mistake, but amazingly deceptive results.
The image_map was never rotated x*90, and I think it was just shifted so that it
didn't extend up that far.   :|


> My intuitive answer to 'Does that ever happen' would be an emphatic
> "No". However... I am no fan of Sketchup and thus do not know what kind
> of quaint things may happen.

I'm not using Sketchup, I'm just using the web-based Height Mapping tool to get
the grayscale map.   Then Google Maps to get the satellite and street maps.


Still having a bit of a struggle getting the overlay textures aligned to the
topolgy, but perhaps some more searching and experimenting will give me good
results that are easily reproduced with other locations.


Posting progress over on pbi

http://news.povray.org/povray.binaries.images/thread/%3Cweb.5ce356f7d68a971b4eec112d0%40news.povray.org%3E/


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