From a8e354c7fad70eb7fdfda62ec83faf1be6c4ed44 Mon Sep 17 00:00:00 2001
From: Samo Penic <samo.penic@gmail.com>
Date: Tue, 24 Jan 2023 20:03:01 +0000
Subject: [PATCH] Changes in code and README for easier compilation. May break something

---
 src/energy.c |   24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/energy.c b/src/energy.c
index 7c29c0b..b182a87 100644
--- a/src/energy.c
+++ b/src/energy.c
@@ -44,9 +44,12 @@
 	return TS_SUCCESS;
 };
 
-/** @brief Calculation of energy of the vertex
+/** @brief Calculation of the bending energy of the vertex.
  *  
- *  Main function that calculates energy of the vertex \f$i\f$. Nearest neighbors (NN) must be ordered in counterclockwise direction for this function to work.
+ *  Main function that calculates energy of the vertex \f$i\f$. Function returns \f$\frac{1}{2}(c_1+c_2-c)^2 s\f$, where \f$(c_1+c_2)/2\f$ is mean curvature,
+ * \f$c/2\f$ is spontaneous curvature and \f$s\f$ is area per vertex \f$i\f$.
+ *
+ * Nearest neighbors (NN) must be ordered in counterclockwise direction for this function to work.
  *  Firstly NNs that form two neighboring triangles are found (\f$j_m\f$, \f$j_p\f$ and common \f$j\f$). Later, the scalar product of vectors \f$x_1=(\mathbf{i}-\mathbf{j_p})\cdot (\mathbf{i}-\mathbf{j_p})(\mathbf{i}-\mathbf{j_p})\f$, \f$x_2=(\mathbf{j}-\mathbf{j_p})\cdot  (\mathbf{j}-\mathbf{j_p})\f$  and \f$x_3=(\mathbf{j}-\mathbf{j_p})\cdot (\mathbf{i}-\mathbf{j_p})\f$  are calculated. From these three vectors the \f$c_{tp}=\frac{1}{\tan(\varphi_p)}\f$ is calculated, where \f$\varphi_p\f$ is the inner angle at vertex \f$j_p\f$. The procedure is repeated for \f$j_m\f$ instead of \f$j_p\f$ resulting in \f$c_{tn}\f$.
  *  
 \begin{tikzpicture}{
@@ -181,6 +184,7 @@
 #endif
 // c is forced curvature energy for each vertex. Should be set to zero for
 // normal circumstances.
+/* the following statement is an expression for $\frac{1}{2}\int(c_1+c_2-c_0^\prime)^2\mathrm{d}A$, where $c_0^\prime=2c_0$ (twice the spontaneous curvature)  */
     vtx->energy=0.5*s*(vtx->curvature/s-vtx->c)*(vtx->curvature/s-vtx->c);
 
     return TS_SUCCESS;
@@ -209,18 +213,18 @@
 }
 
 ts_double direct_force_energy(ts_vesicle *vesicle, ts_vertex *vtx, ts_vertex *vtx_old){
-	if(fabs(vtx->c)<1e-15) return 0.0;
+	if(fabs(vtx->direct_interaction_force)<1e-15) return 0.0;
 //	printf("was here");
 	if(fabs(vesicle->tape->F)<1e-15) return 0.0;
 
 	ts_double norml,ddp=0.0;
 	ts_uint i;
 	ts_double xnorm=0.0,ynorm=0.0,znorm=0.0;
-	/*find normal of the vertex as average normal of all the triangles surrounding it. */
+	/*find normal of the vertex as sum of all the normals of the triangles surrounding it. */
 	for(i=0;i<vtx->tristar_no;i++){
-			xnorm=vtx->tristar[i]->xnorm;
-			ynorm=vtx->tristar[i]->ynorm;
-			znorm=vtx->tristar[i]->znorm;
+			xnorm+=vtx->tristar[i]->xnorm;
+			ynorm+=vtx->tristar[i]->ynorm;
+			znorm+=vtx->tristar[i]->znorm;
 	}
 	/*normalize*/
 	norml=sqrt(xnorm*xnorm+ynorm*ynorm+znorm*znorm);
@@ -228,9 +232,13 @@
 	ynorm/=norml;
 	znorm/=norml;
 	/*calculate ddp, perpendicular displacement*/
-	ddp=xnorm*(vtx->x-vtx_old->x)+xnorm*(vtx->y-vtx_old->y)+znorm*(vtx->z-vtx_old->z);
+	ddp=xnorm*(vtx->x-vtx_old->x)+ynorm*(vtx->y-vtx_old->y)+znorm*(vtx->z-vtx_old->z);
 	/*calculate dE*/
 //	printf("ddp=%e",ddp);
 	return vesicle->tape->F*ddp;		
 	
 }
+
+void stretchenergy(ts_vesicle *vesicle, ts_triangle *triangle){
+	triangle->energy=vesicle->tape->xkA0/2.0*pow((triangle->area/vesicle->tlist->a0-1.0),2);
+}

--
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