added back formula

pedestrian.hpp

@@ -7,13 +7,21 @@ enum Color { BLACK, WHITE };
 
 struct Pedestrian {
   Color color;
+  // $\vec{v}_{\alpha}(t)$
   Vector2d curr_vel; // v_alpha  (actual, ≤ v_max)
+  // $\vec{w}_{\alpha}$
   Vector2d w;        // w_alpha  (preferred, integrates force)
+  // $\vec{r}_\alpha(t)$
   Vector2d curr_pos;
+  // $\vec{e}_{\alpha}(t)$
   Vector2d e;
+  // $v_{\alpha}^{max} = 1.3 v^{0}_{\alpha}$
   double v_max;
+  // $v_\alpha^0$
   double desired_v0;
+  // $\vec{r}^0_\alpha$
   Vector2d destination;
+  // social force
   Vector2d f_i;
 
   Pedestrian() : color(WHITE), curr_vel(0.0, 0.0), w(0.0, 0.0), curr_pos(0.0, 0.0), e(0.0, 0.0), v_max(0.0), desired_v0(0.0), destination(0.0, 0.0), f_i(0.0, 0.0) {}