Hi.

I would like to place something on the surface of a height field, how
would I do this? Specifically I would like to model the Great Wall of
China, any thoughts? Any good tutorials or sample scene files I could
peruse?

-thanks

-paul
-- 

Paul Daniel Jones
307 Chandlee Laboratory
Penn State Chemistry Dept.
pdj### [at] psuedu
http://glasssgi.chem.psu.edu
(814)-865-2090

          C
        /  \
       N    N
       |  O |
       C    C
      / \  / \
  H3C     C    CH3

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Paul Jones wrote:
> 
> Hi.
> 
> I would like to place something on the surface of a height field, how
> would I do this? Specifically I would like to model the Great Wall of
> China, any thoughts? Any good tutorials or sample scene files I could
> peruse?
> 
> -thanks
> 
> -paul

In general: Using megapov's hf_height_at function.  Building a wall mostly
depends, how you build it, whether you place the single stones using while
loops/macros or you use some different construction.  

Christoph

--
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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In article <397F27BE.5847C69C@psu.edu>, Paul Jones <pdj### [at] psuedu> 
wrote:

> I would like to place something on the surface of a height field, how
> would I do this?

The easiest and most robust way to do this is to use the trace() 
function in MegaPOV. This function allows you to find the intersection 
of a ray with an object...just trace a ray straight down at the height 
field from above the point where you want to place an object, and you 
can get the exact position as well as the surface normal("up" direction) 
at that point.
There is also a hf_height_at keyword, but this is not as useful: it 
doesn't give the normal, and it only works with height fields.


> Specifically I would like to model the Great Wall of China, any 
> thoughts? Any good tutorials or sample scene files I could peruse?

This sounds interesting...you might try creating a spline {} with the 
points from trace(), and have the wall follow that, instead of having it 
directly follow the surface of the ground. Or you might be able to do it 
with an isosurface...that might be faster rendering, and can give good 
results.
There is at least one stone wall macro in povray.binaries.scene-files, 
you might want to have a look at that for ideas. I'm sure there are 
other stone/brick macros out there.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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On Wed, 26 Jul 2000 14:02:38 -0400 Paul Jones <pdj### [at] psuedu> wrote:

>I would like to place something on the surface of a height field, how
>would I do this? Specifically I would like to model the Great Wall of
>China, any thoughts? Any good tutorials or sample scene files I could
>peruse?

  Have you seen Glenn McCarter's IRTC entry, "dpatrol.jpg", from the
Jan-Feb 1998 "Great Engineering Achievements" topic? His scene features
the Great Wall of China, with a view extending to the horizon. I'm
looking at it on my IRTC CD-ROM Year Three (shameless plug). Glenn used
separate height fields for each mountain but used sPatch to create the
Wall itself. I'm not sure how he achieved placement of the Wall and
guard towers. He was using POV-Ray v3.0.

http://www.irtc.org

-- 
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer

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