Le_Forgeron <jgr### [at] freefr> wrote:
> Le 26/10/2010 23:38, Mr nous fit lire :
> > Hi There is something that I try to understand every once in a while with
> > povray:
> > I am trying to have a sky sphere with gradient but still with an alpha layer
> > fully transparent in the end image. How do you do that?
> >
> > I try using two rgbt colors, both with a transmit value of 1 as entries to the
> > colormap.
> >
> > If I do that,  only the last entry of color map of my gradient will be used as
> > if the the first entry had never existed. so it seems like the transparency is
> > baked into the color for each entry. could there be an option to make it so that
> > if the first entry has transmit 1 its color is still retained and all
> > transparencies
> > only applied in the alpha layer?
> >
> >
> >
> Could we have a minimal demo scene ? please.

Here it is:



#declare shader_Material = finish {
 brilliance 1.8
 phong 0.5
 phong_size 25.2
 diffuse 0.8 0
 ambient 1
 emission 0
 conserve_energy
}

#declare camLocation  = <7.481132, -6.507640, 5.343665>;
#declare camLookAt = <63.559295, 0.619768, 46.691945>;
camera {
 location  <0, 0, 0>
 look_at  <0, 0, -1>
 right <-1.77777777778, 0, 0>
 up <0, 1, 0>
 angle  49.134343
 rotate  <63.559295, 0.619768, 46.691945>
 translate <7.481132, -6.507640, 5.343665>
}
light_source {
 < 0,0,0 >
 color rgb<2, 2, 2>
 fade_distance 5.999997
 fade_power 2
 matrix <-0.290865, 0.955171, -0.055189,  -0.771101, -0.199883, 0.604525,
0.566393, 0.218391, 0.794672,  4.076245, 1.005454, 5.903862>
}
mesh2 {
 vertex_vectors {
  8,
  <1.000000, 1.000000, -1.000000>,
  <1.000000, -1.000000, -1.000000>,
  <-1.000000, -1.000000, -1.000000>,
  <-1.000000, 1.000000, -1.000000>,
  <1.000000, 0.999999, 1.000000>,
  <0.999999, -1.000001, 1.000000>,
  <-1.000000, -1.000000, 1.000000>,
  <-1.000000, 1.000000, 1.000000>
  }
 normal_vectors {
  6,
  <1.000000, -0.000000, 0.000000>,
  <0.000000, -0.000000, 1.000000>,
  <0.000000, 0.000000, -1.000000>,
  <-0.000000, -1.000000, -0.000000>,
  <-1.000000, 0.000000, -0.000000>,
  <0.000000, 1.000000, 0.000000>
  }
 texture_list {
  1
  texture {
    pigment {rgbft<0.8, 0.8, 0.8, 0, 0>}finish {shader_Material}
    pigment {rgbft<0.8, 0.8, 0.8, 0, 0>}finish {shader_Material}
  }
 }
 face_indices {
  12,
  <0,1,2>, 0,0,0,
  <0,2,3>, 0,0,0,
  <4,7,6>, 0,0,0,
  <4,6,5>, 0,0,0,
  <0,4,5>, 0,0,0,
  <0,5,1>, 0,0,0,
  <1,5,6>, 0,0,0,
  <1,6,2>, 0,0,0,
  <2,6,7>, 0,0,0,
  <2,7,3>, 0,0,0,
  <4,0,3>, 0,0,0,
  <4,3,7>, 0,0,0
  }
 normal_indices {
  12,
  <2,2,2>,
  <2,2,2>,
  <1,1,1>,
  <1,1,1>,
  <0,0,0>,
  <0,0,0>,
  <3,3,3>,
  <3,3,3>,
  <4,4,4>,
  <4,4,4>,
  <5,5,5>,
  <5,5,5>
  }
 interior { ior 1.000000
 caustics 0.1
 }
 matrix <1.000000, 0.000000, 0.000000,  0.000000, 1.000000, 0.000000,  0.000000,
0.000000, 1.000000,  0.000000, 0.000000, 0.000000>
}
sky_sphere {
 pigment {
  gradient y
  color_map {
   [0.0 rgbt<0.33, 0, 0.528, 1>]
   [1.0 rgbt<0.481, 0.774, 0.645, 1>]
  }
 }
}
global_settings {
 max_trace_level 7
 ambient_light rgb<0, 0, 0>
}

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