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Nathan Kopp <Nat### [at] Kopp com> wrote:
> It's not really a bug, just a mis-understanding. You see, the UV-mapping
> implemented here simply maps the X and Y of the texture to the U and V of
> the object. It takes a slice of the texture from the XY plane (Z=0) and
> wraps that slice around the object.
>
> Any slice of gradient z parallel to the XY plane will have a uniform color,
> since the texture will only change in the z direction.
>
> -Nathan
>
Oh, I see: a mis-understanding indeed. But also a bit disappointed.
Couldn't you use a slice of the texture from the XZ plane and wrap that
around the object for gradient z (this is also true for the mandel
pattern).
Well that explains it for the sphere, lathe and box objects. But there
is still a problem with the bicubic_patch object. With gradient x the
gradient goes in the z-direction. With gradient y it goes in the
x-direction
Just render the scene below and you will see the problem.
//******** Scene with uv_mapping bug ? *************
// Change Obj_Switch for different objects
#declare Obj_Switch = 2; // 2= Bicubic_patch
#declare C_Map =
color_map {
[ 0.0 color rgb < 1.0, 1.0, 1.0 > ]
[ 0.3 color rgb < 1.0, 1.0, 1.0 > ]
[ 0.3 color rgb < 1.0, 0.0, 0.0 > ]
[ 0.6 color rgb < 1.0, 0.0, 0.0 > ]
[ 0.6 color rgb < 0.211505, 0.530358, 0.728481 > ]
[ 1.0 color rgb < 0.211505, 0.530358, 0.728481 > ]
}
#if (Obj_Switch = 2)
#declare Object =
bicubic_patch {
type 1 flatness 0.0 u_steps 4 v_steps 3
< -0.6, -1, 0.5 >, < -0.33, 0.0, 0.5 >, <
0.33 , 0.0, 0.5 >, < 0.5, -1, 0.6 >,
< -0.5, 0.0, 0.33 >, < -0.33, -0.2, 0.33 >,
< 0.33, -0.2, 0.33 >, < 0.5, 0.0, 0.33 >,
< -0.5, 0.0, -0.33 >, < -0.33, -0.2, -0.33 >,
< 0.33, -0.2, -0.33 >, < 0.5, 0.0, -0.33 >,
< -0.6, -1, -0.5 >, < -0.33, 0.0, -0.5 >,
< 0.33, 0.0, -0.5 >, < 0.5, -1, -0.6 >
translate y*0.6
}
#end
//Top row with classic gradient
object {
Object
pigment { gradient x color_map { C_Map } scale 0.5 }
translate <-1.3, 0.4, 0.6>
}
object {
Object
pigment { gradient y color_map { C_Map } scale 0.5 }
translate <0, 0.4, 0.6>
}
object {
Object
pigment { gradient z color_map { C_Map } scale 0.5 }
translate <1.3, 0.4, 0.6>
}
//Lower row with uv_mapping
object {
Object
uv_mapping
pigment { gradient x color_map { C_Map } scale 0.5 }
translate <-1.3, -0.6, 0>
}
object {
Object
uv_mapping
pigment { gradient y color_map { C_Map } scale 0.5 }
translate <0, -0.6, 0>
}
object {
Object
uv_mapping
pigment { gradient z color_map { C_Map } scale 0.5 }
translate <1.3, -0.6, 0>
}
camera {
location < 0.0, 3, -5 >
angle 40
look_at < 0.0, 0.0, 0.0 >
}
light_source { <0, 50, -60> rgb 1.5 }
--
e-mail:sme### [at] skynet be
http://users.skynet.be/smellenbergh
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