"geep999" <nomail@nomail> wrote in message 
news:web.4bd5f848f8049eb1380f8080@news.povray.org...
> "Rarius" <rar### [at] rariuscouk> wrote:
>> I did a similar image of Mars a year or so back, but rather than creat a
>> mesh, I used the image to create a pigment function and from that an
>> isosurface. Effectively I created a spherical heightfield. It renders 
>> quite
>> fast and doesn't use that much memory. It also has the added benefit that 
>> I
>> can exagerate the relief in code without rebuilding the mesh.
>>
>> Rarius
> That's interesting. I did experiment a bit with heightfields, but couldn't
> figure out how to wrap it onto a sphere. I'll have to read up about 
> isosurfaces.
> My original aim was to create a high resolution image and make an 
> animation
> of an orbit around the moon. But this needs too much memory, I reckon 
> nearly
> 64Gb. Effectively I split the DEM data of the moon into about 14 strips 
> North to
> South, rendered each separately and combined the resulting images 
> together. Each
> strip used about 3.5Gb RAM, so I guess the whole moon would need 14 x 3.5 
> =
> 49Gb. If using an isosurface will let me get everything into my 4Gb I'd be
> pleased.
> Cheers,
> Peter

Peter,

You are welcome to my source code if it can be any help.

#local pl_radius = 3396;
#local min_alt = -8.208;
#local max_alt = 21.249;
#local alt_fct = max_alt - min_alt;

#local f_relief =
function
{
  pigment
  {
    image_map { gif "mars_topo.gif" once interpolate 2}
    warp { spherical }
    scale<-1, 1, 1>
    rotate<90, 0, 0>
  }
}
isosurface
{
  function { f_sphere(x,y,z,pl_radius+min_alt) - 
alt_fct*f_relief(x,y,z).gray }
  contained_by { box { -4000,4000 } }
  accuracy 0.002
  max_gradient 2
}

Rarius

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