updated compute repulsive effects from border

forces.cpp

@@ -116,13 +116,17 @@ void compute_repulsive_effects_from_borders(Sidewalk &S, Pedestrian *p)
     //
     // $\vectorarrow{F}_{\alpha B}(\vectorarrow{r}_{\alpha B}) = \frac{U^0_{\alpha B}}{R} e^{- \Arrowvert \vectorarrow{r}_{\alpha B} \Arrowvert / R} \frac{\vectorarrow{r}_{\alpha B}}{\Arrowvert \vectorarrow{r}_{\alpha B} \Arrowvert}$
     //
-    double e = 2.718;
+    // double e = 2.718;
+    // we could just use exp
 
     // $\vectorarrow{r}_{\alpha B}$
     Vector2d r_ab = p->curr_pos - obstacle;
     // $\Arrowvert \vectorarrow{r}_{\alpha B} \Arrowvert$
     double r_ab_norm = r_ab.norm();
-
-    p->F_i += *w(get_desired_direction(*p), *-1);
+    if (r_ab_norm < 1e-6)
+      continue;
+    // repulsive force vector (Direction * Magnitude) (Edquation 6)
+    Vector2d f_ab = (r_ab / r_ab_norm) * (U0_AB / R) * exp(-r_ab_norm / R);
+    p->F_i += f_ab * w(get_desired_direction(*p), f_ab * -1);
   }
 }