Add new OffsetSpring force and implement a wobbly patch.

1 files changed, 120 insertions, 11 deletions

diff --git a/akamaru.c b/akamaru.c
index 17c70e9..2ee99ad 100644
--- a/akamaru.c
+++ b/akamaru.c
@@ -27,7 +27,7 @@
 #include <math.h>
 
 const double ground_level = 500;
-const double elasticity = 0.7;
+const double elasticity = 0.8;
 
 typedef struct _xy_pair Point;
 typedef struct _xy_pair Vector;
@@ -39,6 +39,7 @@ typedef struct _Object Object;
 typedef struct _Stick Stick;
 typedef struct _String String;
 typedef struct _Spring Spring;
+typedef struct _OffsetSpring OffsetSpring;
 typedef struct _Polygon Polygon;
 typedef struct _Offset Offset;
 typedef struct _Model Model;
@@ -75,6 +76,11 @@ struct _Spring {
   int length;
 };
 
+struct _OffsetSpring {
+  Object *a, *b;
+  int dx, dy;
+};
+
 struct _Polygon {
   int num_points;
   Point *points;
@@ -93,6 +99,8 @@ struct _Model {
   Offset *offsets;
   int num_springs;
   Spring *springs;
+  int num_offset_springs;
+  OffsetSpring *offset_springs;
   int num_polygons;
   Polygon *polygons;
   double k;
@@ -169,7 +177,6 @@ model_init_polygons (Model *model)
 
   polygon_init_rectangle (&model->polygons[4], 300, 320, 400, 350);
 
-
   model->num_polygons = num_polygons;
 }
 
@@ -295,13 +302,13 @@ model_init_curtain (Model *model)
 static void
 model_init_grid (Model *model)
 {
-  const int num_ropes = 10;
-  const int num_rope_objects = 10;
+  const int num_ropes = 4;
+  const int num_rope_objects = 4;
   const int num_objects = num_ropes * num_rope_objects;
   const int num_strings = num_ropes * (num_rope_objects - 1) +
     (num_ropes - 1) * num_rope_objects;
-  const int string_length = 10;
-  const int rope_offset = 10;
+  const int string_length = 20;
+  const int rope_offset = 20;
   double x, y;
   int i, j, index, string_index;
 
@@ -385,6 +392,60 @@ model_init_molecule (Model *model)
   }
 }
 
+
+static void
+model_init_wobbly (Model *model)
+{
+  const int width = 6, height = 6;
+  const int num_objects = width * height;
+  const int num_offset_springs = (width - 1) * height + width * (height - 1);
+  const int distance = 30;
+  double x, y;
+  int i, j, object_index, spring_index;
+
+  memset (model, 0, sizeof *model);
+  model->objects = g_new (Object, num_objects);
+  model->num_objects = num_objects;
+  model->offset_springs = g_new (OffsetSpring, num_offset_springs);
+  model->num_offset_springs = num_offset_springs;
+  model->k = 0.6;
+
+  model_init_polygons (model);
+
+  object_index = 0;
+  spring_index = 0;
+  for (i = 0; i < width; i++) {
+    for (j = 0; j < height; j++) {
+      x = 200 + i * distance;
+      y = 40 + j * distance;
+      model->objects[object_index].position.x = x;
+      model->objects[object_index].position.y = y;
+      model->objects[object_index].previous_position.x = x;
+      model->objects[object_index].previous_position.y = y;
+      model->objects[object_index].mass = 0.3;
+
+      if (i + 1 < width) {
+	model->offset_springs[spring_index].a = &model->objects[object_index];
+	model->offset_springs[spring_index].b = &model->objects[object_index + height];
+	model->offset_springs[spring_index].dx = distance;
+	model->offset_springs[spring_index].dy = 0;
+	spring_index++;
+      }
+      
+      if (j + 1 < height) {
+	model->offset_springs[spring_index].a = &model->objects[object_index];
+	model->offset_springs[spring_index].b = &model->objects[object_index + 1];
+	model->offset_springs[spring_index].dx = 0;
+	model->offset_springs[spring_index].dy = distance;
+	spring_index++;
+      }
+
+      object_index++;
+    }
+  }
+}
+
+
 static void
 model_fini (Model *model)
 {
@@ -400,6 +461,7 @@ model_accumulate_forces (Model *model)
 {
   int i;
   double x, y, dx, dy, distance, displacement;
+  Point middle;
   Vector u;
 
   for (i = 0; i < model->num_objects; i++) {
@@ -421,6 +483,26 @@ model_accumulate_forces (Model *model)
     model->springs[i].b->force.x -= u.x * model->k * displacement;
     model->springs[i].b->force.y -= u.y * model->k * displacement;
   }
+
+  for (i = 0; i < model->num_offset_springs; i++) {
+    middle.x = 
+      (model->offset_springs[i].a->position.x + 
+       model->offset_springs[i].b->position.x) / 2;
+    middle.y = 
+      (model->offset_springs[i].a->position.y + 
+       model->offset_springs[i].b->position.y) / 2;
+
+    x = middle.x - model->offset_springs[i].dx / 2;
+    y = middle.y - model->offset_springs[i].dy / 2;
+
+    dx = x - model->offset_springs[i].a->position.x;
+    dy = y - model->offset_springs[i].a->position.y;
+
+    model->offset_springs[i].a->force.x += dx * model->k;
+    model->offset_springs[i].a->force.y += dy * model->k;
+    model->offset_springs[i].b->force.x -= dx * model->k;
+    model->offset_springs[i].b->force.y -= dy * model->k;
+  }
 }
 
 static void
@@ -436,9 +518,9 @@ model_integrate (Model *model, double step)
     y = o->position.y;
     
     o->position.x =
-      x + 0.8 * (x - o->previous_position.x) + o->force.x * step * step;
+      x + 0.9 * (x - o->previous_position.x) + o->force.x * step * step;
     o->position.y =
-      y + 0.8 * (y - o->previous_position.y) + o->force.y * step * step;
+      y + 0.9 * (y - o->previous_position.y) + o->force.y * step * step;
 
     o->previous_position.x = x;
     o->previous_position.y = y;
@@ -610,7 +692,7 @@ model_step (Model *model, double delta_t)
   model_accumulate_forces (model);
   model_integrate (model, delta_t);
 
-  for (i = 0; i < 500; i++)
+  for (i = 0; i < 50; i++)
     model_constrain (model);
 
   model->theta += delta_t;
@@ -750,6 +832,31 @@ draw_springs (cairo_t *cr,
 }
 
 static void
+draw_offset_springs (cairo_t *cr,
+		     Model   *model,
+		     Color   *color)
+{
+  int i;
+
+  cairo_set_source_rgba (cr, color->red, color->green, color->blue, 0.4);
+  cairo_new_path (cr);
+  cairo_set_line_width (cr, 2);
+  cairo_set_line_join (cr, CAIRO_LINE_JOIN_ROUND);
+  cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
+
+  for (i = 0; i < model->num_offset_springs; i++) {
+    cairo_move_to (cr,
+		   model->offset_springs[i].a->position.x,
+		   model->offset_springs[i].a->position.y);
+    cairo_line_to (cr,
+		   model->offset_springs[i].b->position.x,
+		   model->offset_springs[i].b->position.y);
+  }
+
+  cairo_stroke (cr);
+}
+
+static void
 draw_polygons (cairo_t *cr, Model *model, Color *color)
 {
   Polygon *p;
@@ -812,6 +919,7 @@ draw_model (GtkWidget *widget, Model *model)
   draw_strings (cr, model, &green);
   draw_springs (cr, model, &black);
   draw_offsets (cr, model, &blue);
+  draw_offset_springs (cr, model, &blue);
   draw_objects (cr, model, &red);
 
   cairo_destroy (cr);
@@ -911,7 +1019,8 @@ create_model_store (void)
     { "Snake", model_init_snake },
     { "Curtain", model_init_curtain },
     { "Grid", model_init_grid },
-    { "Molecule", model_init_molecule }
+    { "Molecule", model_init_molecule },
+    { "Wobbly", model_init_wobbly }
   };
 
   GtkTreeIter iter;
@@ -1087,7 +1196,7 @@ main (int argc, char *argv[])
   closure.model = &model;
   closure.frame_count = 0;
   gettimeofday (&closure.start, NULL);
-  g_timeout_add (100, timeout_callback, &closure);
+  g_timeout_add (40, timeout_callback, &closure);
   gtk_main ();
 
   return 0;