Add initial prototype.

3-mid/opengl/source/lean/renderer/opengl-impostor.ads

@@ -0,0 +1,168 @@
+with
+     openGL.Texture,
+     openGL.Visual;
+
+limited
+with
+     openGL.Camera;
+
+package openGL.Impostor
+--
+-- Contains a 2D image of another openGL visual.
+--
+is
+   type Counter is mod 2**32;
+
+   type pixel_Region is
+      record
+         X, Y          : gl.glInt;
+         Width, Height : gl.glSizeI;
+      end record;
+
+
+   type Item is abstract tagged     -- TODO: Make private.
+      record
+         Target                           : openGL.Visual.view;
+         Visual                           : openGL.Visual.view;
+
+         freshen_Count                    : Counter    := 0;
+         freshen_count_update_trigger_Mod : Counter    := 150;
+
+         size_update_trigger_Delta        : gl.glSizeI := 2;
+         expand_X, expand_Y               : Real       := 0.03;
+
+         never_Updated                    : Boolean    := True;
+         is_Valid                         : Boolean    := True;     -- True when rendered target has both width and height > 0.
+                                                                    -- (NB: Always true for simple impostors.)
+         -- Current state.
+         --
+         current_pixel_Region   : pixel_Region;
+
+         current_Width_pixels,
+         current_Height_pixels  : gl.glSizei;
+         current_copy_X_Offset,
+         current_copy_Y_Offset  : gl.glInt := 0;
+         current_copy_X,
+         current_copy_Y         : gl.glInt;
+         current_copy_Width,
+         current_copy_Height    : gl.glSizeI;
+
+         target_camera_Distance                  : Real;
+         target_camera_Distance_less_frame_Count : Real;
+
+         -- Prior state.
+         --
+         prior_pixel_Region    : pixel_Region := (X => 0, Y => 0, Width => gl.glSizeI'First, Height => gl.glSizeI'First);
+         prior_Width_pixels    : gl.glSizei   := 0;
+         prior_Height_pixels   : gl.glSizei   := 0;
+
+         prior_target_Rotation : Matrix_3x3   := Identity_3x3;
+         prior_target_Position : Vector_3     := [0.0,  0.0,  0.0];
+
+         prior_camera_Position : Vector_3     := [1.0,  1.0,  1.0];
+
+         is_Terrain            : Boolean      := False;
+      end record;
+
+   type View  is access all Item'Class;
+   type Views is array (Positive range <>) of View;
+
+
+   ---------
+   --- Forge
+   --
+
+   procedure destroy (Self : in out Item);
+   procedure free    (Self : in out View);
+
+
+   --------------
+   --- Attributes
+   --
+
+   procedure set_Target (Self : in out Item;   Target : in Visual.view);
+   function  get_Target (Self : in     Item)        return Visual.view;
+
+   procedure Visual_is  (Self : in out Item;   Now    : in Visual.view);
+   function  Visual     (Self : access Item)        return Visual.view;
+
+
+   function current_Camera_look_at_Rotation (Self : in     Item) return Matrix_3x3
+                                             is abstract;
+
+   function update_Required                 (Self : access Item;    the_Camera : access Camera.item'Class) return Boolean
+                                             is abstract;
+   --
+   -- NB: Caches current pixel_Region as a side-effect.
+
+
+   function is_Valid                        (Self : in     Item'Class) return Boolean;
+   --
+   -- True when rendered target has width and height greater than 0.
+
+
+   function never_Updated                   (Self : in     Item'Class) return Boolean;
+   --
+   -- True when 'update' has never been called for the impostor.
+
+
+   function frame_Count_since_last_update   (Self : in     Item'Class) return Natural;
+
+
+   function target_camera_Distance          (Self : in     Item'Class) return Real;
+   --
+   -- Returns the distance from the camera to the target, when 'update_required' was last called.
+
+
+   -- Update trigger configuration.
+   --
+
+   procedure set_freshen_count_update_trigger_Mod (Self : in out Item;   To : in Positive);
+   function  get_freshen_count_update_trigger_Mod (Self : in     Item)    return Positive;
+   --
+   -- Periodic freshen trigger.
+
+   procedure set_size_update_trigger_Delta        (Self : in out Item;   To : in Positive);
+   function  get_size_update_trigger_Delta        (Self : in     Item)    return Positive;
+   --
+   -- Update due to change in size of targets pixel rectangle.
+
+
+   -- Base class subprograms
+   --
+
+   function  is_Transparent (Self : in     Item) return Boolean;
+   procedure set_Alpha      (Self : in out Item;   Alpha        : in Real);
+
+   function  face_Count     (Self : in     Item) return Natural;
+
+
+   procedure pre_update     (Self : in out Item;   the_Camera   : access Camera.item'Class)
+   is abstract;
+
+   procedure update         (Self : in out Item;   the_Camera   : access Camera.item'Class;
+                                                   texture_Pool : in     texture.Pool_view);
+   --
+   -- Renders the impostor to a cleared framebuffer and copies the image to the impostors texture.
+
+   procedure post_update    (Self : in out Item;   the_Camera   : access Camera.item'Class)
+   is abstract;
+
+
+
+private
+
+   function get_pixel_Region (Self : access Item'Class;   camera_Spin                 : in Matrix_3x3;
+                                                          camera_Site                 : in Vector_3;
+                                                          camera_projection_Transform : in Matrix_4x4;
+                                                          camera_Viewport             : in linear_Algebra_3d.Rectangle) return pixel_Region;
+   --
+   -- Calculate and return the smallest rectangular screen region which encloses the target, when rendered by the_Camera.
+
+
+   function general_Update_required (Self : access Item;   the_Camera_Site  : in Vector_3;
+                                                           the_pixel_Region : in pixel_Region) return Boolean;
+   function size_Update_required    (Self : access Item;   the_pixel_Region : in pixel_Region) return Boolean;
+
+
+end openGL.Impostor;