Tweaking.

[akamaru] / akamaru.c

diff --git a/akamaru.c b/akamaru.c
index 8dc477cc0f2ee4b7c10edb92f2828ef2102a2333..8a9e587b40e66da2259011549be4fd2e97820e14 100644 (file)
--- a/akamaru.c
+++ b/akamaru.c
@@ -24,6 +24,8 @@
 #include "akamaru.h"
 
 const double elasticity = 0.7;
+const double friction = 1;
+const double gravity = 20;
 
 void
 polygon_init (Polygon *p, int num_points, ...)
@@ -101,11 +103,18 @@ model_accumulate_forces (Model *model)
   int i;
   double x, y, dx, dy, distance, displacement;
   Point middle;
-  Vector u;
+  Vector u, v;
 
   for (i = 0; i < model->num_objects; i++) {
+    /* Gravity */
     model->objects[i].force.x = 0;
-    model->objects[i].force.y = 3 * model->objects[i].mass;
+    model->objects[i].force.y = gravity * model->objects[i].mass;
+
+    /* Friction */
+    v.x = model->objects[i].position.x - model->objects[i].previous_position.x;
+    v.y = model->objects[i].position.y - model->objects[i].previous_position.y;
+    model->objects[i].force.x -= v.x * friction;
+    model->objects[i].force.y -= v.y * friction;
   }
 
   for (i = 0; i < model->num_springs; i++) {
@@ -142,6 +151,15 @@ model_accumulate_forces (Model *model)
     model->offset_springs[i].b->force.x -= dx * model->k;
     model->offset_springs[i].b->force.y -= dy * model->k;
   }
+
+  for (i = 0; i < model->num_objects; i++) {
+    double f = 
+      model->objects[i].force.x * model->objects[i].force.x +
+      model->objects[i].force.y * model->objects[i].force.y;
+
+    if (f > 1000000)
+      abort();
+  }
 }
 
 static void
@@ -157,9 +175,9 @@ model_integrate (Model *model, double step)
     y = o->position.y;
     
     o->position.x =
-      x + 0.9 * (x - o->previous_position.x) + o->force.x * step * step;
+      x + (x - o->previous_position.x) + o->force.x * step * step;
     o->position.y =
-      y + 0.9 * (y - o->previous_position.y) + o->force.y * step * step;
+      y + (y - o->previous_position.y) + o->force.y * step * step;
 
     o->previous_position.x = x;
     o->previous_position.y = y;
@@ -330,7 +348,6 @@ model_step (Model *model, double delta_t)
 
   model_accumulate_forces (model);
   model_integrate (model, delta_t);
-
   for (i = 0; i < 50; i++)
     model_constrain (model);