No, that can't be the reasoning for the darkness increase.  Something else must
be going on.  I'd have expected a problem with filter and because I knew about
Nathan's changes I wouldn't have thought transmit would be the thing that is
different from the official versions.  Even if you were to consider transmit and
filter behaviour to be switched in the official versions (bear with me please, I
know it isn't) to explain why the darkening occurs I'd still think filtering
should not be such a tremendous change just because one more layer is added.
Seems to be related to layering onto a layered texture that's doing it.
I tested this ought again and if a layers of image maps is declared first then
put in as the base layer of the plane texturing then it's fine, no problems.
However if layering of the usual pigments (pattern, no pattern) is declared and
added in as the base texture to the plane then it breaks down.
Something must be wrong (or never meant to be) in official then, but check for
yourselves.  Here's what I was doing:

// #version 3.1;
// unofficial MegaPov 0.4;

global_settings {
        max_trace_level 5
}

#include "colors.inc"
#include "stones.inc"

light_source { 10*y color rgb 1}
camera {
  location  <0,9,9>
  angle 67
  look_at   0
}

#declare Layer1=
        texture { // base
                pigment {rgb <1,1,1>
                      //  image_map {gif "test.gif" transmit 0, 1}
        // translate -.5 scale 6 rotate 90*x
         }
                }
        texture {
                pigment {rgbf <0,1,0,1>
                     //   image_map {gif "test.gif" transmit 0, 1}
        // translate 0 scale 6 rotate 90*x rotate 90*y
        }
                }

plane {y,0
        texture {Layer1 // using this instead of the Stone17 texture
        //        pigment {image_map {gif "test.gif" transmit 0, 1}
       // translate 0 scale 6 rotate 90*x rotate 90*y}
                // T_Stone17
                }
        texture {
                pigment {image_map {gif "test.gif" transmit 0, 1}
         translate -.5 scale 6 rotate 90*x}
                }
}


Bob

"Chris Huff" <chr### [at] yahoocom> wrote in message
news:chrishuff_99-6D5671.10202927022000@news.povray.org...
| In article <38B93A53.83D12556@pacbell.net>, lin### [at] povrayorg
| wrote:
|
| > In the official version layered textures that use filter or transmit
| > react the same i.e. they both default to the behavior of filter. In
| > MegaPov Nathan changed this so that transmit works "correctly" or so
| > he claims. It's not really a bug as much as it is a dissagreement as
| > to what the correct behavior should be where layered textures are
| > concerned. I do not know at this point if this change will be reflected
| > in POV-Ray v3. or not. It will definately break a lot of pre v3.5
| > textures if it is implememnted though the #version directive can be
| > used to compensate for this.
|
| Actually, it is filter that acts like transmit in layered textures in
| the official version. MegaPOV fixes it so filter acts like filter and
| transmit like transmit(makes more sense, doesn't it?). Since it is
| documented in the manual, it can't really be considered a bug, so I call
| it a "documented mis-feature". :-)
|
| And converting older textures is actually quite easy: just set the
| filter in the upper layers to 0 and add the value that was there to the
| transmit value. This should give the same appearance as it had in the
| official version. Or you could use the #version directive...
|
| --
| Chris Huff
| e-mail: chr### [at] yahoocom
| Web page: http://chrishuff.dhs.org/

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