star-sim

commit 3fe09681e47e02ed6abdcc719a8d8b3a4f80da09
parent b1b317c4bdfcc45519c6aae3ab50c474a274f13b
Author: Amin Mesbah <mesbahamin@gmail.com>
Date:   Fri, 16 Jun 2017 22:40:28 -0700

Fix center-of-mass calculation.

Diffstat:
M
barnes_hut.h
 | 
17
++++++++++-------

1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/barnes_hut.h b/barnes_hut.h
@@ -237,20 +237,21 @@ void quad_tree_set_virtual_stars(struct QuadTreeNode *node, struct Star virtual_
     }
     else if (*current_num < max_virtual_stars)
     {
-        // TODO: handle mass more intelligently
         float x_sum = 0;
         float y_sum = 0;
         float mass_sum = 0;
 
         for (int i = 0; i < node->cell->num_stars; ++i)
         {
-            x_sum += node->cell->stars[i]->x;
-            y_sum += node->cell->stars[i]->y;
-            mass_sum += node->cell->stars[i]->mass;
+            struct Star *s = node->cell->stars[i];
+
+            mass_sum += s->mass;
+            x_sum += s->x * s->mass;
+            y_sum += s->y * s->mass;
         }
 
-        float x_avg = x_sum / node->cell->num_stars;
-        float y_avg = y_sum / node->cell->num_stars;
+        float x_avg = x_sum / mass_sum;
+        float y_avg = y_sum / mass_sum;
 
         virtual_stars[*current_num].x = x_avg;
         virtual_stars[*current_num].y = y_avg;
@@ -259,7 +260,9 @@ void quad_tree_set_virtual_stars(struct QuadTreeNode *node, struct Star virtual_
     }
     else
     {
-        printf("Virtual_stars buffer overflow.\n");
+        printf("Virtual_stars buffer overflow:\n\tcurrent_num: %d\n\tmax_virtual_stars: %d\n",
+            *current_num,
+            max_virtual_stars);
     }
 }