Hi all,




I got DEM data about this region and converted them to a PNG file (color, 16
bits w/ value split by red and green corposants). I put a scale of 65535 in
Y direction as the value of the DEM is directly in meter and, according to
the POV documentation, the maximum value of 16 bits (65535) correspond to 1
for POV.

The size of this PNG is 512 * 512 and as the DEM file scale is 75 meters by


I use following test script:
**********
#include "colors.inc"
#include "textures.inc"

// Parametres
#declare vue =  <-8700, 500, 12525>; // D'ou regarde-t-on
#declare cible = <-3450, 628, 10125>; // Vers ou
#declare echelle = 38400; // Echelle a applique sur les MNT

light_source{ <-40000,100000,-50000> White }

#declare terrain = height_field {
 png "tst.png"
 smooth
 translate <-.5, 0, -.5>
 scale <echelle,65535,echelle>

 pigment {
  slope y
  color_map {
   [0 White]
   [0.60 SteelBlue*0.1]
   [0.65 White*2]
   [0.7 Gray95]
   [0.75 Gray80]
   [0.85 MediumForestGreen]
   [1 ForestGreen]
  }
 }
}

camera {
 location vue
 look_at cible
}


object {terrain} // Il faut tracer le terrain

sky_sphere {
 pigment {
  gradient y
  color_map {
   [ 0.5
     color CornflowerBlue ]
   [ 1.0  color MidnightBlue ]
  }
  scale 2
  translate -1
 }
 pigment {
  bozo
  turbulence 0.65
  octaves 6
  omega 0.7
  lambda 2
  color_map {
   [0.0 0.1 color rgb <0.85, 0.85, 0.85>
      color rgb <0.75, 0.75, 0.75>]
   [0.1 0.5 color rgb <0.75, 0.75, 0.75>
      color rgbt <1, 1, 1, 1>]
   [0.5 1.0 color rgbt <1, 1, 1, 1>
      color rgbt <1, 1, 1, 1>]
  }
  scale <0.2, 0.5, 0.2>
 }

 rotate x*90
}

**********



Does someone know which parameter I can change to resolve this problem ?


loading ?

Thanks and regards.

Laurent

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> #declare echelle = 38400; // Echelle a applique sur les MNT
>  scale <echelle,65535,echelle>

You seem to have uneven scaling, have you been trying to make the mountains
taller?

> Unfortunately, mountains appear flattened on the POV image and I think
it's
> because far objects appear smaller compared with the reality .
> Does someone know which parameter I can change to resolve this problem ?

Orthagraphic(spelt right?) camera stops distance based scaling I think

Post a reply to this message

Hi Josh,

"Josh" <som### [at] microsoftcom> wrote:
> > #declare echelle = 38400; // Echelle a applique sur les MNT
> >  scale <echelle,65535,echelle>
>
> You seem to have uneven scaling, have you been trying to make the mountains
> taller?

No, it's because the scale depends on my PNG file for X & Z direction and
depend on the max number of colors (65535) on the Y direction.

So, a "real" box of 1x1x1 meter in my PNG file should create a 1x1x1 box in
my POV world.

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To explain better my problem, please have a look on a real photo :

http://mamaf.online.fr/Annecy/image13.htm

And now my POV image (almost from the same point of view) :

http://destroyedlolo.homeunix.org:8080/~laurent/Lac.jpg

As you can see, the little hill in the 1st plan is quite ok but the big 
mountain on the background looks very very flattened.

Thanks for any help

Laurent

Post a reply to this message

destroyedlolo wrote:
> To explain better my problem, please have a look on a real photo :
> 
> http://mamaf.online.fr/Annecy/image13.htm
> 
> And now my POV image (almost from the same point of view) :
> 
> http://destroyedlolo.homeunix.org:8080/~laurent/Lac.jpg
> 
> As you can see, the little hill in the 1st plan is quite ok but the big 
> mountain on the background looks very very flattened.
> 
> Thanks for any help
> 
> Laurent


Hi Laurent, the photo is using a very long focal length lens which 
compresses distance and exaggerates perspective. Looks like an 700mm or 
higher lens.

One of the POV gurus may know how to convert standard camera focal 
lengths into POV statements, but I don't :-(

You should read sections 2.3.1.1.3, 2.3.1.1.4, and  2.3.1.1.5 of the 
POV-Ray docs about camera angles and distance.  If its possible, you may 
be able to do it with just the direction & angle keywords, or else try 
moving your camera further back and use a smaller angle.

RG

Post a reply to this message

Hi Gonzo,

gonzo wrote:
> 
> Hi Laurent, the photo is using a very long focal length lens which 
> compresses distance and exaggerates perspective. Looks like an 700mm or 
> higher lens.

... and it's also what my eyes show ;-D


> 
> One of the POV gurus may know how to convert standard camera focal 
> lengths into POV statements, but I don't :-(

I'll try in the advanced user NG also.

> You should read sections 2.3.1.1.3, 2.3.1.1.4, and  2.3.1.1.5 of the 
> POV-Ray docs about camera angles and distance.  If its possible, you may 
> be able to do it with just the direction & angle keywords, or else try 
> moving your camera further back and use a smaller angle.

I make some other tests using angles (and w/ a better point of view).

* The image without specifying any "angle" : 
http://destroyedlolo.homeunix.org:8080/~laurent/sans_angle.jpg

* The same with "angle 38" :
http://destroyedlolo.homeunix.org:8080/~laurent/angle_38.jpg

The result is better but ... you have to know the original view to 
recognize the mountains :-(

The other point is if I continue to reduce "Angle", I have also to move 
my camera further and it's bad because there is other mountains in my back.

Bye

Laurent

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