add Stan Melax' ImplicitCloth demo

examples/Experiments/ImplicitCloth/stan/SpringNetwork.h

@@ -0,0 +1,63 @@
+#ifndef STAN_SPRING_NETWORK_H
+#define STAN_SPRING_NETWORK_H
+
+#include "vec3n.h"
+
+#define SPRING_STRUCT (0)
+#define SPRING_SHEAR  (1)
+#define SPRING_BEND   (2)
+
+
+class SpringNetwork
+{
+ public:
+       class Spring
+       {
+        public:
+               int type;          // index into coefficients spring_k[]
+               float restlen;
+               int a,b;      // spring endpoints vector indices
+               int iab,iba;  // indices into off-diagonal blocks of sparse matrix
+               Spring(){}
+               Spring(int _type,int _a,int _b,float _restlen):type(_type),a(_a),b(_b),restlen(_restlen){iab=iba=-1;}
+       };
+       Array<Spring> springs;
+       float3N     X;    // positions of all points
+       float3N     V;    // velocities
+       float3N     F;    // force on each point
+       float3N     dV;   // change in velocity
+       float3Nx3N  A;    // big matrix we solve system with
+       float3Nx3N  dFdX; // big matrix of derivative of force wrt position
+       float3Nx3N  dFdV; // big matrix of derivative of force wrt velocity
+       float3Nx3N  S;    // used for our constraints - contains only some diagonal blocks as needed S[i,i]
+       int awake;
+       float3 bmin,bmax;
+       union
+       {
+               struct
+               {
+                       float spring_struct;
+                       float spring_shear;
+                       float spring_bend;
+               };
+               float spring_k[3];
+       };
+       float  spring_damp;
+       float  spring_air;
+       float  cloth_step;  // delta time for cloth
+       float3 cloth_gravity;
+       float  cloth_sleepthreshold;
+       int    cloth_sleepcount;
+
+       SpringNetwork(int _n);
+       Spring &AddBlocks(Spring &s);
+       Spring &CreateSpring(int type,int a,int b,float restlen){return AddBlocks(springs.Add(Spring(type,a,b,restlen)));}
+       Spring &CreateSpring(int type,int a,int b){return CreateSpring(type,a,b,magnitude(X[b]-X[a]));}
+       void    UpdateLimits() { BoxLimits(X.element,X.count,bmin,bmax);}
+       void    Wake(){awake=cloth_sleepcount;}
+       void    Simulate(float dt);
+       void    PreSolveSpring(const Spring &s);
+       void    CalcForces();
+};
+
+#endif //STAN_SPRING_NETWORK_H