Subject:
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Re: Teardrops
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Newsgroups:
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lugnet.cad.ray
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Date:
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Thu, 14 Nov 2002 16:59:48 GMT
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Viewed:
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1140 times
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In lugnet.cad.ray, Dave Schuler writes:
> In lugnet.cad.ray, Bram Lambrecht writes:
> > Try creating a lathe object using a quadratic or cubic spline.
> > http://www.povray.org/documentation/view/48/
>
> I tried messing around with lathe objects, but I was having trouble
> approximating the character of the curve.
I gave this a shot... I pretty familiar with bezier curves from using them in
CorelDraw, so I used a bezier_spline. Basically, for every segment you want,
you create 4 points. The first and last points are the endpoints of the
segment, and the middle two points are the "control points." The line that
would connect the endpoint with it's control point becomes the tangent to the
curve, and the length of that line determines the curvature. For a circle, the
length should be about half of the radius. Here's what I came up with:
------------------ Begin File ----------------------
// Teardrop lathe object using bezier curves....
// Set edit=true to see the control points for the bezier curve
// Set edit=false to see the final lathe object
#declare edit=true;
#include "colors.inc"
#if(edit)
camera {
orthographic
up <0, 5, 0>
right <5, 0, 0>
location <2.5, 2.5, -100>
look_at <2.5, 2.5, 0>
}
#else
background{White}
camera {
angle 10
location <1, 10, -50>
look_at <0, 2, 0>
}
light_source {
<20, 20, -20> color White
}
#end
#declare Red_Point = <0.00, 0.00>;
#declare Yellow_Point = <0.50, 0.00>;
#declare Green_Point = <1.00, 0.50>;
#declare Blue_Point = <1.00, 1.00>;
#declare Yellow_Point2= <1.00, 2.00>;
#declare Green_Point2 = <0.00, 2.00>;
#declare Red_Point2 = <0.00, 3.50>;
#if(edit)
cylinder { Red_Point, Red_Point - <0,0,20>, .1 pigment { Red }
finish { ambient 1 } }
cylinder { Yellow_Point, Yellow_Point - <0,0,20>, .1 pigment { Yellow }
finish { ambient 1 } }
cylinder { Green_Point, Green_Point - <0,0,20>, .1 pigment { Green }
finish { ambient 1 } }
cylinder { Blue_Point, Blue_Point- <0,0,20>, .1 pigment { Blue }
finish { ambient 1 } }
cylinder { Red_Point2, Red_Point2 - <0,0,20>, .1 pigment { Red }
finish { ambient 1 } }
cylinder { Yellow_Point2, Yellow_Point2 - <0,0,20>, .1 pigment { Yellow }
finish { ambient 1 } }
cylinder { Green_Point2, Green_Point2 - <0,0,20>, .1 pigment { Green }
finish { ambient 1 } }
#end
lathe {
bezier_spline
8,
Red_Point, Yellow_Point, Green_Point, Blue_Point
Blue_Point, Yellow_Point2, Green_Point2, Red_Point2
#if(edit)
pigment { White }
finish { ambient 1 }
#else
pigment { Blue }
#end
}
------------------ End File ----------------------
Hope that helps!
--Bram
Bram Lambrecht
bram@cwru.edu
www.bldesign.org
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Message is in Reply To:
 | | Re: Teardrops
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| (...) approximating the character of the curve. Orion emailed me a pointer to the Glob_5 shape in one of the POV-Ray .inc files, and that was quite a help. I played with the vertex sequence, but my liberal arts brain turns to mush when dealing with (...) (22 years ago, 14-Nov-02, to lugnet.cad.ray)
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