Utilisation : Les liens ne sont pas apparents. Pour obtenir des informations sur un mot clé, cliquez-le dans le script !

// Persistence of Vision Raytracer Version 3.5 Scene Description File
// File: tracevines.pov
// Author: Ron Parker
// Description: Algorithm shamelessly lifted from
// "Modeling Plants With Environment-Sensitive Automata"
// Proceedings of Ausgraph '88, pages 27-33
// by James Arvo and David Kirk

#macro Interfere(A, B, Object)
	#local N = <0, 0, 0>;
	#local I = trace(Object, A, B-A, N);
	(vlength(N) & (vlength(I-A)<vlength(B-A)))
#end

#macro FindTmp(CurPt, Normal, Object, RandSeed)
	#local More = 1;
	#local Safety = C3;
	#local Q = <0, 0, 0>;
	#while (More & Safety)
		// select random unit T orthogonal to Normal
		#local T = <rand(RandSeed)-.5, rand(RandSeed)-.5, rand(RandSeed)-.5>;
		#local T = T-vdot(T, Normal)*Normal;
		#if (vlength(T))
			#local T = T/vlength(T);
			#local Safety = Safety-1;
			#local Q = CurPt + C2 * T;
			#local More = Interfere(CurPt, Q, Object);
		#end
	#end
	#if (Safety)
		Q;
	#else
		<0, 0, 0>;
	#end
#end

#macro Draw(CurPt, NewPt, Normal, NewNormal)
	union {
		sphere {CurPt, R1}
		sphere {NewPt, R1}
		cylinder {CurPt, NewPt, R1}
		#local Pr = vcross(NewPt-CurPt, NewNormal);
		#local Pl = vnormalize(NewPt-CurPt);
		#local Or = vnormalize(.3*NewNormal+.7*Pl);
		triangle {NewPt, NewPt+LL*Or, NewPt+.5*LL*Or+.5*LW*Pr
			translate R1*NewNormal}
		triangle {NewPt, NewPt+LL*Or, NewPt+.5*LL*Or-.5*LW*Pr
			translate R1*NewNormal}
		texture {pigment {color green 1}}
	}
#end

#macro Grow(Start, Normal, Object, RandSeed)
	#local Continue = 1;
	#while (Continue)
		#ifndef (Watchdog)
			#local Watchdog = C8;
		#else
			#declare Watchdog = Watchdog - 1;
		#end
		#ifndef (Gen)
			#local Gen = 0;
		#else
			#local Gen2 = Gen+1;
			#local Gen = Gen2;
		#end
		#local Continue = 0;
		#local Branch = 0;
		#if (Watchdog)
			#local CurPt = Start + C1 * Normal;
			#local NewTmp = FindTmp(CurPt, Normal, Object, RandSeed)
			#if (vlength(NewTmp))
				#local Dist = 9999;
				#local NewRoot = Start;
				#local NewNormal = Normal;
				#local NewPt = CurPt;
				#local Iter = C3;
				#while (Iter)
					#local R = <rand(RandSeed)-.5, rand(RandSeed)-.5, rand(RandSeed)-.5>+Bias;
					#local N = <0, 0, 0>;
					#local Int = trace(Object, NewTmp, R, N);
					#if (vlength(N))
						#local CurDist = vlength(Int-Start);
						#local TestPt = Int + C1 * N;
						#if ((CurDist < Dist) & (CurDist < C4) & !Interfere(CurPt, TestPt, Object))
							#local Dist = CurDist;
							#local NewRoot = Int;
							#local NewNormal = vnormalize(N);
							#local NewPt = Int+ C1 * N;
						#end	// if shorter dist
					#end
					#local Iter = Iter-1;
				#end
				#if (vlength(CurPt-NewPt))
					Draw(CurPt, NewPt, Normal, NewNormal)
					#if (rand(RandSeed) > C5 & Gen < C7)
						#local Continue = 1;
						#if (rand(RandSeed)<C6)
							#local Branch = 1;
						#end
					#end	// if continue
				#end	// if new point
			#end	// if NewTmp found
		#end	// if watchdog
		#if (Branch)
			Grow(NewRoot, NewNormal, Object, RandSeed)
		#end	// if branch
		#local Start = NewRoot;
		#local Normal = NewNormal;
	#end	// while continue
#end

#declare Fence = union {
	cylinder {-2.2*x, <-2.2, 2, 0>, .2}
	cylinder {0, <0, 2, 0>, .2}
	cylinder {2.2*x, <2.2, 2, 0>, .2}
	cylinder {<2.2, 1.7, 0> <-2.2, 1.7, 0> .1}
	cylinder {<2.2, 1, 0> <-2.2, 1, 0> .1}
	plane {y 0 pigment {bozo color_map {[0 rgb <1, .8, .5>][1 rgb <.8, .5, .1>]}}}
	translate -.02*y
	texture {pigment {color rgb <.5, .25, .1>}}
}

#declare C1 = .02;	// distance of the vine from the object it grows on
#declare C2 = .05;	// Approximate step distance
#declare C3 = 60;	// number of attempts to find a surface to take root
#declare C4 = .1;	// Maximum jump between roots
#declare C5 = .05;	// probability of quitting after each generation
#declare C6 = .3;	// probability of branching after each generation
#declare C7 = 150;	// absolute maximum generations
#declare C8 = 10000;	// absolute maximum generations along all branches
#declare R1 = .01;	// radius of vine
#declare LL = .1;	// length of leaf
#declare LW = .1;	// width of leaf
#declare Bias = <-.2, .4, 0>;
#declare RandSeed = seed(347);

#declare Sa = array[12] {
	<-2, 0, 0>, <-2.4, 0, 0>, <-2.2, 0, .2>, <-2.2, 0,-.2>,	// left post
	<2, 0, 0>, <2.4, 0, 0>, <2.2, 0, .2>, <2.2, 0,-.2>,	// right post
	<-.2, 0, 0>, <.2, 0, 0>, <0, 0, .2>, <0, 0,-.2>	// center post
}

#declare Na = array[12] {x,-x, z,-z,-x, x, z,-z,-x, x, z,-z}
#declare Count = 0;

#while (Count<12)
	#debug concat("plant ", str(Count+1, 0, 0), "\n")
	Grow(Sa[Count], Na[Count], Fence, RandSeed)
	#declare Count = Count+1;
#end

object {Fence}
light_source {<-20, 20,-20> rgb 1}
camera {location <-2, 3,-5> look_at y}

Et voici ce que nous obtenons :