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Rendering a gradient with uv_mapping seems to have a bug when
using the gradient pattern: no mapping is done with gradient z ! With
gradient x and gradient y it renders fine. This is the case with the
sphere, lathe and box objects.
Rendering a bicubic_patch with uv_mapping has a problem with all
gradients. With gradient x the gradient goes in the z-direction. With
gradient y it goes in the x-direction and with gradient z no mapping is
done.
Rendering the scene below will show the problem. The top row shows
gradient x, gradient y and gradient z with the 'classic' gradient.
The bottom row shows the same gradients with uv_mapping.
//************** Scene with uv_mapping bug ? *************
// Change Obj_Switch for different objects
#declare Obj_Switch = 0; //0 =Sphere; 1= Lathe; 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 = 0)
#declare Object = sphere { < 0.0, 0.0, 0.0 >, 0.5 }
#end
#if (Obj_Switch = 1)
#declare Object =
lathe {
quadratic_spline
6,
<0.0, 0.000000 >,
<0.00000, 0.00645 >,
<0.86452, 0.09677 >,
<0.28387, 0.35484 >,
<0.24516, 0.48 >,
<0.00000, 1.00645 >
scale <0.7, 0.8, 0.7>
}
#end
#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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