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- POV-Ray Tutorial
Loops in POV-Ray
1. For + While
Comparison
2. Linear
Transformations
3. Circular
Transformations
4. Moebius etc.
5. Screws
& Spirals
6. Twisting
Spirals
>7. Snails
& Ammonites
8. Spherical Spirals 1
9. Spherical Spirals 2
10. Fibonacci Spirals
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Loops for Snails and Ammonites
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In the last exsamples of a spiral the spheres had always the same size.
Now we will see how to reduce continually the size of the spheres, the radius and the
height of the screwing of a snail:
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//-------------------------------------
#declare Ball =
sphere{<0,0,0>,0.5
texture{pigment{color
rgb<1,0.65,0.0>}
finish {phong 1}}}
#declare Radius0=3.0;// basic radius
#declare NR=9;//number of revolutions
#declare NpR=100;//number elements p.r.
#declare Scale=0.75; //per revolution
#declare HpR=0.8;//difference in y p.r.
//-------------------------------------
#local Hd = HpR/NpR;
#local Scale_p = pow(Scale,1/360);
#local Scale_pE = pow(Scale_p,360/NpR);
#local Old_S = Scale_pE;
#local Old_H = Hd;
#declare Nr = 0; //start
#declare EndNr = NR*NpR; // end
#while (Nr< EndNr)
object{Ball
translate<Radius0,0,0>
scale Old_S
translate<0,Old_H,0>
rotate<0,Nr*360/NpR,0>}
#declare Nr = Nr+1; // next Nr
#declare Old_S =Scale_pE*Old_S;
#declare Old_H =Old_H+Hd*Old_S;
#end // ------------ end of loop ----- |
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If we reduce the height of the screwing to zero,
we get the classic form of
"Ammonitus povrayensis":
//-----------------------------------
#declare Ball =
sphere{<0,0,0>,1.0
texture{...see above...}}}
#declare Radius0 = 3.5;
#declare NR = 9;//number of revolutions
#declare NpR=50;//number of elem.p.r.
#declare Scale = 0.55; //per revolution
#declare HpR = 0.00;
//------------------------------------ |
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By scaling the shape of the basic element and
texturing it with stone or granit textures
it is possible to form nearly every shape of
a snailhouse or ammonite you wish:
For example: what about a
"Turritella turris var. povensis"?
//---------------------------------
#declare Ball =
sphere{<0,0,0>,0.70
scale <1,1.5,1>
texture{T_Stone3 scale 1.5
finish {phong 0.3}}}
#declare Radius0 = 1.5;
#declare NR=9.1;
//number of revolutions
#declare NpR = 30;
//number of elements per revolution
#declare Scale=0.78;
//per revolution
#declare HpR = 1.6;
//--------------------------------- |
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