Add new Spacer constraint and a 'dock' model.

3 files changed, 85 insertions, 3 deletions

diff --git a/akamaru.c b/akamaru.c
index 22b2477..ae01a27 100644
--- a/akamaru.c
+++ b/akamaru.c
@@ -69,6 +69,14 @@ offset_spring_init (OffsetSpring *spring, Object *a, Object *b,
 }
 
 void
+spacer_init (Spacer *spacer, Object *a, Object *b, double length)
+{
+  spacer->a = a;
+  spacer->b = b;
+  spacer->length = length;
+}
+
+void
 polygon_init (Polygon *p, int num_points, ...)
 {
   double dx, dy, length;
@@ -91,7 +99,7 @@ polygon_init (Polygon *p, int num_points, ...)
   p->normals = g_new (Vector, p->num_points);
   /* Compute outward pointing normals.  p->normals[i] is the normal
    * for the edged between p->points[i] and p->points[i + 1]. */
- for (i = 0; i < p->num_points; i++) {
+  for (i = 0; i < p->num_points; i++) {
     j = (i + 1) % p->num_points;
     dx = p->points[j].x - p->points[i].x;
     dy = p->points[j].y - p->points[i].y;
@@ -131,6 +139,7 @@ model_fini (Model *model)
     g_free (model->offsets[i].objects);
   g_free (model->springs);
   g_free (model->offset_springs);
+  g_free (model->spacers);
   for (i = 0; i < model->num_polygons; i++)
     g_free (model->polygons[i].points);
   g_free (model->polygons);
@@ -359,6 +368,22 @@ model_constrain (Model *model)
     model->strings[i].b->position.y = y + dy * (1 - fraction);
   }
 
+  /* Spacer constraints. */
+  for (i = 0; i < model->num_spacers; i++) {
+    x = model->spacers[i].a->position.x;
+    y = model->spacers[i].a->position.y;
+    dx = model->spacers[i].b->position.x - x;
+    dy = model->spacers[i].b->position.y - y;
+    distance = estimate_distance (dx, dy, model->spacers[i].length);
+    if (distance > model->spacers[i].length)
+      continue;
+    fraction = (distance - model->spacers[i].length) / distance / 2;
+    model->spacers[i].a->position.x = x + dx * fraction;
+    model->spacers[i].a->position.y = y + dy * fraction;
+    model->spacers[i].b->position.x = x + dx * (1 - fraction);
+    model->spacers[i].b->position.y = y + dy * (1 - fraction);
+  }
+
   /* Stick constraints. */
   for (i = 0; i < model->num_sticks; i++) {
     x = model->sticks[i].a->position.x;
@@ -389,7 +414,7 @@ model_step (Model *model, double delta_t)
 
   model_accumulate_forces (model);
   model_integrate (model, delta_t);
-  for (i = 0; i < 50; i++)
+  for (i = 0; i < 2; i++)
     model_constrain (model);
 
   model->theta += delta_t;
diff --git a/akamaru.h b/akamaru.h
index 9b544ae..1646a34 100644
--- a/akamaru.h
+++ b/akamaru.h
@@ -12,6 +12,7 @@ typedef struct _Stick Stick;
 typedef struct _String String;
 typedef struct _Spring Spring;
 typedef struct _OffsetSpring OffsetSpring;
+typedef struct _Spacer Spacer;
 typedef struct _Polygon Polygon;
 typedef struct _Offset Offset;
 typedef struct _Model Model;
@@ -53,6 +54,11 @@ struct _OffsetSpring {
   int dx, dy;
 };
 
+struct _Spacer {
+  Object *a, *b;
+  int length;
+};
+
 struct _Polygon {
   int num_points;
   Point *points;
@@ -73,6 +79,8 @@ struct _Model {
   Spring *springs;
   int num_offset_springs;
   OffsetSpring *offset_springs;
+  int num_spacers;
+  Spacer *spacers;
   int num_polygons;
   Polygon *polygons;
   double k;
@@ -90,6 +98,7 @@ void offset_spring_init (OffsetSpring *spring,
 void spring_init (Spring *spring, Object *a, Object *b, double length);
 void stick_init (Stick *stick, Object *a, Object *b, double length);
 void string_init (String *string, Object *a, Object *b, double length);
+void spacer_init (Spacer *spacer, Object *a, Object *b, double length);
 
 void polygon_init (Polygon *p, int num_points, ...);
 void polygon_init_diamond (Polygon *polygon, double x, double y);
diff --git a/main.c b/main.c
index 2423b4f..39cb5ad 100644
--- a/main.c
+++ b/main.c
@@ -261,6 +261,53 @@ model_init_wobbly (Model *model)
   }
 }
 
+static void
+model_init_dock (Model *model)
+{
+  const int num_objects = 8;
+  const int num_spacers = (num_objects - 1) * (num_objects - 2) / 2;
+  const int num_springs = num_objects - 1;
+  const int distance = 30;
+  double x, y;
+  int i, j;
+  Object *object;
+  Spring *spring;
+  Spacer *spacer;
+
+  memset (model, 0, sizeof *model);
+  model->objects = g_new (Object, num_objects);
+  model->num_objects = num_objects;
+  model->springs = g_new (Spring, num_springs);
+  model->num_springs = num_springs;
+  model->spacers = g_new (Spacer, num_spacers);
+  model->num_spacers = num_spacers;
+  model->k = 0.1;
+
+  model_init_polygons (model);
+  model->polygons = g_new (Polygon, 1);
+  polygon_init_rectangle (&model->polygons[0], -400, 300, 1400, 350);
+  model->num_polygons = 1;
+
+
+  object = model->objects;
+  spring = model->springs;
+  spacer = model->spacers;
+  for (i = 0; i < num_objects; i++, object++) {
+    x = 200 + i * distance / 3;
+    y = 40;
+    object_init (object, x, y, 1);
+    if (i == 0)
+      continue;
+    spring_init (spring++,
+		 &model->objects[0],
+		 &model->objects[i],
+		 distance);
+    for (j = 1; j < num_objects - i; j++) {
+      spacer_init (spacer++, object, object + j, distance);
+    }
+  }
+}
+
 typedef struct _Color Color;
 struct _Color {
   double red, green, blue;
@@ -554,7 +601,8 @@ create_model_store (void)
     { "Curtain", model_init_curtain },
     { "Grid", model_init_grid },
     { "Molecule", model_init_molecule },
-    { "Wobbly", model_init_wobbly }
+    { "Wobbly", model_init_wobbly },
+    { "Dock", model_init_dock }
   };
 
   GtkTreeIter iter;