POV-Ray: Newsgroups: povray.general: hi~, everybody, how to modulate two bmp files with the third bmp file?: hi~, everybody, how to modulate two bmp files with the third bmp file?

POV-Ray : Newsgroups : povray.general : hi~, everybody, how to modulate two bmp files with the third bmp file? : hi~, everybody, how to modulate two bmp files with the third bmp file?		Server Time 1 Aug 2024 22:16:50 EDT (-0400)

From: lien0n
Date: 10 Mar 2005 03:45:00
Message: <web.42300839aa72325b598059850@news.povray.org>

For instance, I.ve got two files "wet.bmp" and "dry.bmp", and the third
file's name is "factor.bmp". All of them are of the same resolution,
256*128 for example.

Now, I want to use them to generate a new pigment. I've got the following:

#declare Wetting=function{ pigment {image_map{sys "wet.bmp"} }}
#declare Drying=function{ pigment {image_map{sys "dry.bmp"} }}
#declare Factor=function{ pigment {image_map{sys "factor.bmp"} }}

plane{z,-0.00001
  pigment {
    image_map {
      function 256 128 { pigment {
        color (1-Factor(x,y,z).gray)*Wetting(x,y,z) +
Drying(x,y,z)*Factor(x,y,z).gray     (*)
      }}
    }
  }
}

But when parsing, error message appears at line (*):
   Parse Error: Float expected but vector or color expression found.
It seems that (x,y,z), I use to locate the pixel, does not work. Maybe i am
still not familiar enough with the syntex of how to use
user-defined-fuction, and maybe there is an other way to implement what i
want to do.

So any advice will be deeply appreciated!

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