POV-Ray : Newsgroups : povray.advanced-users : isosurface issue Server Time: 30 Mar 2020 14:23:25 GMT
  isosurface issue (Message 1 to 1 of 1)  
From: Rick
Subject: isosurface issue
Date: 17 Jan 2020 22:15:01
Message: <web.5e22312e1b58ba452532f13a0@news.povray.org>
Many years ago I created a POV-Ray isosurface model of Mars using the MOLA DEM
in a POV-Ray scene file.  For reference my website illustrates the result of how
I use the isosurface function:
https://martianx.weebly.com/mars-shorelines.html

 The isosurface part of the scene file is as follows:

********
#declare fn_Pigm = function {
    pigment {
      image_map {
        png "MarsDEM2880.png"
         map_type 1
         once
         interpolate 4
      }
   }
  }

*******
isosurface {
 function {f_sphere(x, y, z, 3396.2)+fn_Pigm(x, y, z).gray*-Scale}
 threshold  -Scale/2
 contained_by {sphere {0, 3450}}
 pigment {
        image_map {
         png "colorexpanded-1.png"
         map_type 1
         once
         interpolate 4
      }
   }
   finish {ambient 0.9 diffuse 0.0}
}
******

Orinally, by choosing an appropriate value for “Scale” I could superimpose a
blue sphere ("ocean") and adjust the radius of the “ocean" so that the “ocean”
radius could be set to intersect various “Mars” elevations accurately. In other
words I crested a calibrated model of Mars.

I think it was two POV-Ray versions ago, the calibration no longer produced
accurate results. No choice of the “Scale” value would created a calibrated
Mars.

Any ideas of why the change in operation please respond
to:sto### [at] suddenlinknet


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