Dear

How about this is O.K. or NOT ?

                        color_map
                        {
                            [0.0 0.1 color Blue color Blue]
                            [0.9 1.0 color Yellow color Yellow]
                        } // close color_map

Y.Tanabe
Kobe,Japan


Dawn McKnight wrote:

> So, I'm working on this object.  I won't bore you by telling you what it
> is, or what I'm using it for, or like that, but I will say that I'm
> trying to get a smooth color gradient between the edge and the center,
> which is to say, I need it to be a gradient in both x and z directions,
> constant as per y.
>
> Which sounds like a cylindrical pigment type, to me.  I read the
> documentation, page 262, first paragraph, which says "It starts at 1.0
> at the origin and increases to a maximum [sic] value of 0.0 as it
> approaches a distance of 1 unit from the Y axis.  It remains at 0.0 for
> all areas beyond that distance."
>
> So, if I understand this correctly, if I set a color_map with an entry
> of color Blue at 1.0, and color Yellow at 0.0, I should get a
> cylindrical pattern where the edge is yellow, and the center is blue,
> and in between is interpolated shading... in other words, various shades
> of green.
>
> Well, I don't need a one unit cylindrical pattern... I need one that's
> scaled to an ellipse of about 300x125 units.  So I do the scaling, and
> translate the origin of the pattern to where I need it to be... and...
> Huh.  that's weird.  Instead of interpolated colors, I get an oval of
> blue, with a sharp-edge delineation where it becomes abruptly yellow.
>
> Also, it seems to actually start with 0.0 at the origin, and increase to
> 1.0, in contradiction to the documentation.
>
> Also, if I put in more than two colors, most of the color entries
> disappear... only the lowest value color, and the highest value color, appear.
>
> My code follows, so you can see for yourself what happens when it
> renders.  If someone could confirm for me that this is a bug, or
> alternately, point out to me where I'm making my mistake, I'd be grateful.
>
> /*
> // Persistence of Vision Ray Tracer Scene Description File
> // File: bussard.pov
> // Vers: 3.1
> // Desc: bussard collector for the front of the nacelle
> // Date: 30 Oct '00
> // Last: 4 Nov '00
> // Auth: Dawn McKnight
> */
>
> background { color Black }
>
> light_source { <300, 50, 300> color White }
>
> camera {
>         location <-500, 0, -400>
>         look_at <-500, 0, 0>
>         } // close camera
>
> #local Bus1 = intersection {
>
> prism {
>         quadratic_spline
>         linear_sweep
>         -1, // height 1
>         1, // height 2.. this is just for visualization purposes, I'll extend
> it later.
>         6, // number of control points
>         <200, 100>, <400, -25>, <185, -135>, <0, -25>, <200, 100>, <400, -25>
>         } // close prism
>
>         box {
>                 <214, -2, 120>,
>                 <-10, 2, -25>
>                 } // close box
>
>         } // close intersection
>
>
> #local Bus2 = merge {
>         object { Bus1 }
>         object { Bus1 rotate 180*x translate -49.99*z }
>         } // close merge
>
> #local BusCap = intersection {
>         lathe {
>                 quadratic_spline
>                 4,
>                 <-110, 185>, <0, 0>, <125, 200>, <0, 400>
>                 sturm
>                 //rotate 90*z
>                 } // close lathe
>
>         box {
>                 <-130, -10, -130>,
>                 <130, 214, 0>
>                 } // close box
>
>         } // close intersection
>
> #local BussCut = union {
>         object { Bus2 scale 25*y rotate 90*x rotate 90*z translate 25*x}
>         object { BusCap translate -25*z }
>         object { BusCap rotate 180*y translate 25*z }
>         } // close merge
>
> #local BusShape = merge {
>         object { BussCut }
>         box { <-125, 213.9, -25>, <125, 314, 25> }
>         cylinder { <0, 213.9, -25>, <0, 314, -25>, 125 }
>         cylinder { <0, 213.9, 25>, <0, 314, 25>, 125 }
>         } // close union
>
> light_source {
>         <0, 0, 0>
>         color White
>         looks_like {
>                 BusShape
>                 rotate -90*z
>                 pigment {
>                         cylindrical
>                         scale <300, 125, 125>
>                         translate 300*x
>                         color_map {
>                                 [1.0 color Yellow]
>                                 [0.1 color Blue]
>                                 } // close color_map
>                         } // close pigment
>                 finish { ambient 0.8 diffuse 0.6 }
>                 } // close looks_like
>         rotate 90*x
>         translate <-700, -25, 0>
>         } // close light_source

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