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// Persistence of Vision Ray Tracer Scene Description File
// File: func_gradient.pov
// Vers: 3.5
// Desc: Gradient macros example
// Date: January 2002
// Auth: Christoph Hormann
//
// -w512 -h512 +a0.3
// =============================================================
//
// This scene file demonstrates the vector analysis macros in
// 'math.inc'. In the upper half the basis function is
// displayed. The lower left shows the length of the gradient
// returned by the fn_Gradient() macro. The box on the lower
// right is textured with the directional gradient in y
// direction calculated with the fn_Gradient_Directional()
// macro, positive values in blue color, negative values in
// green color. The whole picture is covered with a
// rectangular grid of arrows pointing in direction of the
// gradient vector and demonstrating use of the vGradient()
// macro.
//
// =============================================================
#version 3.5;
global_settings {
assumed_gamma 1.0
noise_generator 1
}
#default { finish { ambient 1 diffuse 0 } }
camera {
orthographic
location <0,0,1>
look_at <0,0,0>
right 1*x
up 1*y
}
// ------ the basis function for calculating the gradient from ------
#declare fn_test=
function {
pattern {
pigment_pattern {
agate
color_map {
[0.4 rgb 0]
[0.6 rgb 1]
}
scale 0.8
}
}
}
#include "functions.inc"
#include "math.inc"
#declare fn_grad = fn_Gradient(fn_test)
#declare fn_gradDy = fn_Gradient_Directional(fn_test, y )
// ------ lower left quarter ------
box {
<0, -0.5, 0>, <0.5, 0.0, 0>
texture {
pigment {
function { fn_gradDy(x, y, z)*0.004 + 0.5 }
color_map {
[0.15 color rgb y ]
[0.45 color rgb 0 ]
[0.55 color rgb 0 ]
[0.85 color rgb z ]
}
}
}
}
// ------ lower right quarter ------
box {
<-0.5, -0.5, 0>, <0, 0.0, 0>
texture {
pigment {
function { fn_grad(x, y, z)*0.004 }
color_map {
[0.0 color rgb 0.0 ]
[1.0 color rgb 1.0 ]
}
}
}
}
// ------ upper half ------
box {
<-0.5, -0.0, 0>, <0.5, 0.5, 0>
texture {
pigment {
function { fn_test(x, y, z) }
color_map {
[0.0 color rgb 0.0 ]
[1.0 color rgb 1.0 ]
}
}
}
}
#declare PosX=-0.5;
#declare Spacing=0.018;
union {
#while (PosX < 0.5)
#declare PosY=-0.5;
#while (PosY < 0.5)
#declare Pos=<PosX, PosY, 0>;
#declare Vgrd=vGradient(fn_test, Pos);
#declare Vgrd=<Vgrd.x, Vgrd.y, 0>*0.1;
#if (vlength(Vgrd)>0.008)
cylinder {
<PosX, PosY, 0>,
<PosX, PosY, 0>+Vgrd*0.005,
0.002
texture {
pigment { color rgb z*Gradient_Length(fn_test, Pos)*0.01 }
}
}
sphere {
<PosX, PosY, 0>,
0.003
texture {
pigment { color rgb x }
}
}
#end
#declare PosY=PosY+Spacing;
#end
#declare PosX=PosX+Spacing;
#end
}
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