Add initial prototype.

4-high/gel/source/joint/gel-ball_joint.ads

@@ -0,0 +1,107 @@
+with
+     gel.Joint,
+     gel.Sprite,
+
+     physics.Joint.DoF6,
+     physics.Joint.Ball,
+     physics.Space;
+
+package gel.ball_Joint
+--
+--  Allows sprites to be connected via a 'ball and socket' joint.
+--
+is
+   type Item  is new gel.Joint.item with private;
+   type View  is access all Item'Class;
+   type Views is array (math.Index range <>) of View;
+
+
+   Sway  : constant Joint.Degree_of_freedom := 1;     -- TODO: Can we use an enumeration here ?
+   Heave : constant Joint.Degree_of_freedom := 2;
+   Surge : constant Joint.Degree_of_freedom := 3;
+
+   Pitch : constant Joint.Degree_of_freedom := 4;
+   Yaw   : constant Joint.Degree_of_freedom := 5;
+   Roll  : constant Joint.Degree_of_freedom := 6;
+
+
+   package std_physics renames standard.Physics;
+   use Math;
+
+   ----------
+   ---  Forge
+   --
+
+   procedure define  (Self : access Item;   in_Space                : in     std_physics.Space.view;
+                                            Sprite_A,    Sprite_B   : access gel.Sprite.item'Class;
+                                            Pivot_in_A,  Pivot_in_B : in     Vector_3);
+   overriding
+   procedure destroy (Self : in out Item);
+
+
+   --------------
+   --  Attributes
+   --
+
+   overriding
+   function Physics     (Self : in     Item) return gel.joint.Physics_view;
+
+   overriding
+   function Frame_A     (Self : in     Item) return Matrix_4x4;
+   overriding
+   function Frame_B     (Self : in     Item) return Matrix_4x4;
+
+   overriding
+   procedure Frame_A_is (Self : in out Item;   Now : in Matrix_4x4);
+   overriding
+   procedure Frame_B_is (Self : in out Item;   Now : in Matrix_4x4);
+
+   overriding
+   function Degrees_of_freedom (Self : in Item) return joint.Degree_of_freedom;
+
+
+   ----------
+   --- Bounds - limits the range of motion for a degree of freedom.
+   --
+
+   overriding
+   function  is_Bound      (Self : in     Item;   for_Degree : in joint.Degree_of_freedom) return Boolean;
+
+   overriding
+   function  low_Bound     (Self : access Item;   for_Degree : in joint.Degree_of_freedom) return Real;
+   overriding
+   procedure low_Bound_is  (Self : access Item;   for_Degree : in joint.Degree_of_freedom;
+                                                  Now        : in Real);
+
+   overriding
+   function  high_Bound     (Self : access Item;   for_Degree : in joint.Degree_of_freedom) return Real;
+   overriding
+   procedure high_Bound_is (Self : access Item;   for_Degree : in joint.Degree_of_freedom;
+                                                  Now        : in Real);
+
+   overriding
+   function  Extent        (Self : in     Item;   for_Degree : in joint.Degree_of_freedom) return Real;
+
+   overriding
+   procedure Velocity_is   (Self : in     Item;   for_Degree : in joint.Degree_of_freedom;
+                                                  Now        : in Real);
+
+   --------------
+   --- Operations
+   --
+
+   -- Nil.
+
+
+
+private
+
+   type physics_DoF6_Joint_view is access all std_physics.Joint.DoF6.item'Class;
+
+
+   type Item is new GEL.Joint.item with
+      record
+         Physics : access std_physics.Joint.ball.item'Class;
+   end record;
+
+end gel.ball_Joint;