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I am not entirely sure if this has been reported before.
I used povray v3.5b8 on a 750MHz PIII, windows 98
When using sphere_sweep to generate a hollow tube there are
some problems in rendering the inside of the tube.
Strange bands of discontinuous normals seem to appear in areas where
the spheres make a bend.
Below is a 'small' example that shows the problem.
Second point is that I used a parameterization for the sizes
of the spheres that depended on the clock to generate an animation.
It was a rather complex formula. I now use a different method where
I generate an different include file for every frame. The reason
is that this seems to be much faster. Apparently the formula
is computed for every pixel in stead of ones per frame. I
think some caching may improve the speed of rendering.
Andrel
----
#version 3.5;
#include "colors.inc"
global_settings {
assumed_gamma 1.0
}
// ----------------------------------------
camera {
location <0.0, 0.5, -4.0>
direction 1.5*z
right x*image_width/image_height
look_at <0.0, 0.0, 0.0>
}
sky_sphere {
pigment {
gradient y
color_map {
[0.0 rgb <0.6,0.7,1.0>]
[0.7 rgb <0.0,0.1,0.8>]
}
}
}
light_source {
<0, 0, 0> // light's position (translated below)
color rgb <1, 1, 1> // light's color
translate <-0, 5, -10>
}
// ----------------------------------------
plane {
y, -1
pigment { color rgb <0.3,0.7,0.3> }
}
intersection{
sphere_sweep {
catmull_rom_spline
11,
<-0.785398,0.000000,0.000000>,0.684887,
<-0.392699,0.000000,0.000000>,0.747715,
<0.000000,0.000000,0.000000>,0.779126,
<0.342020,0.060307,0.000000>,0.792240,
<0.642788,0.233956,0.000000>,0.797142,
<0.866025,0.500000,0.000000>,0.798889,
<0.984808,0.826352,0.000000>,0.799517,
<0.984808,1.173648,0.000000>,0.799752,
<0.866025,1.500000,0.000000>,0.799843,
<0.642788,1.766044,0.000000>,0.799875,
<0.342020,1.939693,0.000000>,0.799871
}// end sphere_sweep
sphere_sweep {
catmull_rom_spline
11,
<-0.785398,0.000000,0.000000>,0.479132,
<-0.392699,0.000000,0.000000>,0.545101,
<0.000000,0.000000,0.000000>,0.578083,
<0.342020,0.060307,0.000000>,0.591852,
<0.642788,0.233956,0.000000>,0.596999,
<0.866025,0.500000,0.000000>,0.598833,
<0.984808,0.826352,0.000000>,0.599492,
<0.984808,1.173648,0.000000>,0.599739,
<0.866025,1.500000,0.000000>,0.599835,
<0.642788,1.766044,0.000000>,0.599868,
<0.342020,1.939693,0.000000>,0.599865
inverse }// end sphere_sweep
box{<-3.141593,-1,-.15><2,3,1>}
bounded_by{box{<-3.141593,-1,-.15><2.284808,3.3,1>}}
translate x*2.5+y*-3+z*-3
scale .5
rotate x*45+y*40
pigment { color rgb <1,0.2,0.0> }
finish{specular .3}
}// end difference
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