"Kay-Ju" <k.j### [at] gmxde> wrote in message 
news:web.4a448d38b99e86456aaf5a00@news.povray.org...
> Can i use an image_map to create a
> 3D-particle system?
>
> I.e. i have a field consisting of let's say 32
> by 32 small spheres and i want them to be translated
> along the y-axis according to the map-color.
>
> Can this be done?
> In an easy way?
>

You can declare a pigment using the image as an image_map in the pigment 
declaration.
You can use two nested loops to work through the grid positions and use the 
'eval_pigment' function in POV-Rays 'functions.inc' to tell you what the 
color is at that point on the image.
You can then use that color as a height value when adding each sphere to the 
scene.

The default image_map is layed on the X-Y plane, so you'll either need to 
rotate it or you'll need to pass the X and Z positions into the eval_pigment 
function to represent the X and Y coordinates.
By default the image is scaled to 1 unit high and 1 unit wide, so you'll 
need to scale it or factor that into the positions you pass into 
eval_pigment.

If you want to work with large numbers of spheres (e.g. 1000 by 1000), it's 
worth extracting the SDL from the eval_pigment function and placing it 
inline in your scene. You'll find it declares a function and you only need 
to declare that function once rather than a million times, saving 
significant processing time.

Regards,
Chris B.

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