/*
	IMPORTANT Make sure you run this in a NEW database.
	
	I created a new database called MazeGame and then ran 
	the script in there	
*/

CREATE TABLE [dbo].[Games] (
	[UserName] [nvarchar] (100) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
	[LevelName] [varchar] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
	[PositionX] [int] NOT NULL ,
	[PositionY] [int] NOT NULL ,
	[Orientation] [float] NOT NULL 
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[Levels] (
	[LevelName] [varchar] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
	[Maze] [varchar] (8000) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
	[MazeWidth] [int] NOT NULL ,
	[MazeHeight] [int] NOT NULL 
) ON [PRIMARY]
GO

INSERT INTO Levels (LevelName, Maze, MazeWidth, MazeHeight)
	SELECT 'Easy', 
		'11111222' +
		'1S0012E2' +
		'11101101' +
		'10000101' +
		'10111101' +
		'10100101' +
		'10000001' +
		'11111111',
		8,8

GO
CREATE FUNCTION MAX_DISTANCE() RETURNS INT
AS
BEGIN
	RETURN 2147483647
END
GO

CREATE FUNCTION SCREEN_HEIGHT() RETURNS INT
AS
BEGIN
	RETURN 20
END
GO

CREATE FUNCTION SCREEN_WIDTH() RETURNS INT
AS
BEGIN
	RETURN 80
END
GO

CREATE FUNCTION TILE_WIDTH() RETURNS INT
AS
BEGIN
	RETURN 64
END
GO

CREATE FUNCTION WALL_SCALE_VALUE() RETURNS INT
AS
BEGIN
	RETURN 800
END
GO

CREATE FUNCTION fnGetMapChar(
@Maze VARCHAR(8000), 
@MazeWidth INT, 
@MazeHeight INT,
@X FLOAT, 
@Y FLOAT) RETURNS CHAR(1)
BEGIN
	DECLARE @MapX INT
	DECLARE @MapY INT

	SET @MapX = CONVERT(INT, (@X / dbo.TILE_WIDTH()))
	SET @MapY = CONVERT(INT, (@Y / dbo.TILE_WIDTH()))
	
	DECLARE @Offset INT
	
	SET @Offset = (@MazeWidth * @MapY) + @MapX

	DECLARE @Char CHAR(1)

	SET @Char = SUBSTRING(@Maze, @Offset + 1, 1)

	RETURN 	@Char
END
GO

CREATE FUNCTION fnGetScreenOffset(
@X INT,
@Y INT
) RETURNS INT
AS
BEGIN
	RETURN (@Y * dbo.SCREEN_WIDTH()) + @X
END
GO

CREATE FUNCTION fnIsExit(
@Maze VARCHAR(8000), 
@MazeWidth INT, 
@MazeHeight INT,
@X FLOAT, 
@Y FLOAT) RETURNS BIT
BEGIN
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = 'E')
	BEGIN
		RETURN 1
	END
	
	RETURN 0	
END
GO

CREATE FUNCTION fnIsHorizontalWall(
@Maze VARCHAR(8000), 
@MazeWidth INT, 
@MazeHeight INT,
@X FLOAT, 
@Y FLOAT) RETURNS INT
BEGIN
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = '1')
	BEGIN
		RETURN 1
	END
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = '2')
	BEGIN
		RETURN 2
	END
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y - 1) = '1')
	BEGIN
		RETURN 1
	END
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y - 1) = '2')
	BEGIN
		RETURN 2
	END

	RETURN 0
END
GO

CREATE FUNCTION fnIsSolid(
@Maze VARCHAR(8000), 
@MazeWidth INT, 
@MazeHeight INT,
@X FLOAT, 
@Y FLOAT) RETURNS BIT
BEGIN
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = '1'
		OR dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = '2')
	BEGIN
		RETURN 1
	END
	
	RETURN 0	
END
GO

CREATE FUNCTION fnIsVerticalWall(
@Maze VARCHAR(8000), 
@MazeWidth INT, 
@MazeHeight INT,
@X FLOAT, 
@Y FLOAT) RETURNS INT
BEGIN
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = '1')
	BEGIN
		RETURN 1
	END
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X, @Y) = '2')
	BEGIN
		RETURN 2
	END
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X - 1, @Y) = '1')
	BEGIN
		RETURN 1
	END
	IF(dbo.fnGetMapChar(@Maze, @MazeWidth, @MazeHeight, @X - 1, @Y) = '2')
	BEGIN
		RETURN 2
	END

	RETURN 0
END
GO

CREATE FUNCTION fnNormalizeAngle(@Angle FLOAT) RETURNS FLOAT
BEGIN
	WHILE(@Angle < 0)
	BEGIN
		SET @Angle = @Angle + (2*PI());
	END
	
	WHILE(@Angle > 2*PI())
	BEGIN
		SET @Angle = @Angle - (2*PI());
	END
	
	RETURN @Angle;
END
GO

CREATE PROCEDURE spBackwards
AS
-- Position details
DECLARE @PositionX INT
DECLARE @PositionY INT
DECLARE @Orientation FLOAT

-- Level details
DECLARE @Maze VARCHAR(8000)
DECLARE @MazeWidth INT
DECLARE @MazeHeight INT

SELECT 
	@PositionX = PositionX,
	@PositionY = PositionY,
	@Orientation = Orientation,
	@Maze = Maze,
	@MazeWidth = MazeWidth,
	@MazeHeight = MazeHeight
FROM Games
INNER JOIN Levels
	ON Games.LevelName = Levels.LevelName
WHERE Games.UserName = USER_NAME()

IF(@@RowCount = 0)
BEGIN
	RAISERROR('You need to start a new game by calling spNewGame', 16, 1)
	RETURN
END


IF(dbo.fnIsExit(@Maze, @MazeWidth, @MazeHeight, @PositionX, @PositionY) = 1)
BEGIN
	EXEC spRender
	RETURN
END

DECLARE @NewX INT
DECLARE @NewY INT

SET @NewX = @PositionX
SET @NewY = @PositionY

IF(@Orientation = 0)
BEGIN
	SET @NewX = @PositionX - dbo.TILE_WIDTH()
END
ELSE IF(@Orientation = (PI() / 2)) 
BEGIN			
	SET @NewY = @PositionY - dbo.TILE_WIDTH()
END
ELSE IF(@Orientation = PI()) 
BEGIN			
	SET @NewX = @PositionX + dbo.TILE_WIDTH()
END
ELSE
BEGIN
	SET @NewY = @PositionY + dbo.TILE_WIDTH()
END

IF(dbo.fnIsSolid(@Maze, @MazeWidth, @MazeHeight, @NewX, @NewY) = 0)
BEGIN
	SET @PositionX = @NewX
	SET @PositionY = @NewY
END

SET NOCOUNT ON

UPDATE Games SET 
	PositionX = @PositionX, 
	PositionY = @PositionY 
WHERE UserName = USER_NAME()

SET NOCOUNT OFF

EXEC spRender
GO

CREATE PROCEDURE spDrawStrip 
@Screen VARCHAR(8000) OUT, 
@Strip INT, 
@Wall_height INT, 
@Texture CHAR(1)
AS

DECLARE @i INT

IF(@Wall_height < dbo.SCREEN_HEIGHT())
BEGIN
	--for(int i = 0; i < wall_height; i++)
	SET @i = 0
	WHILE(@i < @Wall_height)
	BEGIN
		SET @Screen = STUFF(@Screen, dbo.fnGetScreenOffset(@Strip, @I + ((dbo.SCREEN_HEIGHT() - @Wall_height)) / 2) + 1, 1, @Texture)
		SET @i = @i + 1
	END
END
ELSE
BEGIN
	SET @i = 0
	WHILE(@i < dbo.SCREEN_HEIGHT())
	BEGIN
		SET @Screen = STUFF(@Screen, dbo.fnGetScreenOffset(@Strip, @I) + 1, 1, @Texture)
		SET @i = @i + 1
	END
END
GO

CREATE PROCEDURE spDrawWalls
-- Position details
@PositionX INT,
@PositionY INT,
@Orientation FLOAT,
-- Level details
@Maze VARCHAR(8000),
@MazeWidth INT,
@MazeHeight INT,
-- Screen
@Screen VARCHAR(8000) OUT
AS

SET @Screen = SPACE(dbo.SCREEN_HEIGHT() * dbo.SCREEN_WIDTH()) + 'END'

------------------------------------------------------------------
-- Cast a ray for each strip
------------------------------------------------------------------
DECLARE @Fov FLOAT
DECLARE @RayAngle FLOAT
DECLARE @RayDelta FLOAT

-- The Field of view is set to 100 Degrees. This gives slight fish eye efect when 
-- you look at a wall but gives better visibility
SET @Fov = ((PI()*100)/180)
SET @RayAngle = dbo.fnNormalizeAngle(@Orientation - (@Fov / 2))
SET @RayDelta = @Fov / dbo.SCREEN_WIDTH()

--for(int strip=0; strip < SCREEN_WIDTH; strip++, rayAngle = NormalizeAngle(rayAngle + rayDelta)) 
DECLARE @Strip INT
SET @Strip = 0
WHILE(@Strip < dbo.SCREEN_WIDTH())
BEGIN
	DECLARE @Horizontal_texture INT
	SET @Horizontal_texture = 0
	DECLARE @Horizontal_x FLOAT
	DECLARE @Horizontal_y FLOAT
	DECLARE @Horizontal_step_x FLOAT
	DECLARE @Horizontal_step_y FLOAT
	DECLARE @Vertical_texture INT
	SET @Vertical_texture = 0
	DECLARE @Vertical_x FLOAT
	DECLARE @Vertical_y FLOAT
	DECLARE @Vertical_step_x FLOAT
	DECLARE @Vertical_step_y FLOAT
	
	EXEC spSetupIntersecionParams 
			       @CameraX = @PositionX,
			       @CameraY = @PositionY,
	                       @Angle = @RayAngle,
	                       @Horizontal_x = @Horizontal_x OUT,
	                       @Horizontal_y = @Horizontal_y OUT,
	                       @Horizontal_step_x = @Horizontal_step_x OUT,
	                       @Horizontal_step_y = @Horizontal_step_y OUT,
	                       @Vertical_x = @Vertical_x OUT,
	                       @Vertical_y = @Vertical_y OUT,
	                       @Vertical_step_x = @Vertical_step_x OUT,
	                       @Vertical_step_y = @Vertical_step_y OUT
	
	DECLARE @Horizontal_hit_dist FLOAT
	DECLARE @Vertical_hit_dist FLOAT
	
	
	------------------------------------------------------------------------
	-- find nearest horizontal intersection ...
	------------------------------------------------------------------------
	WHILE(1=1) 
	BEGIN
		IF(@Horizontal_x < 0 OR @Horizontal_x > (@MazeWidth * dbo.TILE_WIDTH()) - 1
			OR @Horizontal_y < 0 OR @Horizontal_y > (@MazeHeight * dbo.TILE_WIDTH()) - 1)
		BEGIN
			---------------------------------------------------------------
			-- We ran out of the map. Set hit distance to maximum and break
			---------------------------------------------------------------
			SET @Horizontal_hit_dist = dbo.MAX_DISTANCE()
			BREAK
		END
		ELSE 
		BEGIN
			SET @Horizontal_texture = dbo.fnIsHorizontalWall(
						@Maze, @MazeWidth, @MazeHeight,
						@Horizontal_x, @Horizontal_y)

			IF(@Horizontal_texture <> 0) 
			BEGIN
				---------------------------------------------------------------
				-- We found a non-zero square. Calculate distance and break
				---------------------------------------------------------------
				SET @Horizontal_hit_dist = SQRT(POWER(@Horizontal_x - @PositionX, 2) +
								POWER(@Horizontal_y - @PositionY, 2))
				BREAK
			END
			ELSE 
			BEGIN
				SET @Horizontal_x = @Horizontal_x + @Horizontal_step_x;
				SET @Horizontal_y = @Horizontal_y + @Horizontal_step_y;
			END
		END
	END
	
	
	------------------------------------------------------------------------
	-- find nearest vertical intersection ...
	------------------------------------------------------------------------
	WHILE(1=1)
	BEGIN
		IF(@Vertical_x < 0 OR @Vertical_x > (@MazeWidth *  dbo.TILE_WIDTH())-1 OR
		   @Vertical_y < 0 OR @Vertical_y > (@MazeHeight * dbo.TILE_WIDTH())-1)
		BEGIN
			---------------------------------------------------------------
			-- We ran out of the map. Set hit distance to maximum and break
			---------------------------------------------------------------
			SET @Vertical_hit_dist = dbo.MAX_DISTANCE()
			BREAK
		END
		ELSE 
		BEGIN
			SET @Vertical_texture = dbo.fnIsVerticalWall(
					@Maze, @MazeWidth, @MazeHeight,
					@Vertical_x, @Vertical_y)

			IF(@Vertical_texture <> 0)
			BEGIN
				---------------------------------------------------------------
				-- We found a non-zero square. Calculate distance and break
				---------------------------------------------------------------
				SET @Vertical_hit_dist = SQRT(
					POWER(@Vertical_x - @PositionX, 2) +
					POWER(@Vertical_y - @PositionY, 2))
				BREAK
			END
			ELSE
			BEGIN
				SET @Vertical_x = @Vertical_x + @Vertical_step_x;
				SET @Vertical_y = @Vertical_y + @Vertical_step_y;
			END
		END
	END


	------------------------------------------------------------------------
	-- compare distances and draw vertical wall strip ...
	------------------------------------------------------------------------
	DECLARE @Wall_height INT
	DECLARE @Texture CHAR(1)

	IF(@Horizontal_hit_dist <= @Vertical_hit_dist) 
	BEGIN
		-- use horizontal intersection
		SET @Wall_height = CONVERT(INT, dbo.WALL_SCALE_VALUE() / @Horizontal_hit_dist)
		
		IF(@Horizontal_texture = 1)
			SET @Texture = '|'
		ELSE
			SET @Texture = 'E'

		EXEC spDrawStrip @Screen = @Screen OUT, @Strip = @Strip, @Wall_height = @Wall_height, @Texture = @Texture
	END
	ELSE
	BEGIN
		-- use vertical intersection
		SET @Wall_height = CONVERT(INT, dbo.WALL_SCALE_VALUE() / @Vertical_hit_dist)
		
		IF(@Vertical_texture = 1)
			SET @Texture = '-'
		ELSE
			SET @Texture = 'E'

		EXEC spDrawStrip @Screen = @Screen OUT, @Strip = @Strip, @Wall_height = @Wall_height, @Texture = @Texture
	END

	-- Move to the next strip
	SET @Strip = @Strip + 1
	SET @RayAngle = dbo.fnNormalizeAngle(@RayAngle + @RayDelta)
END
GO

CREATE PROCEDURE spFowards
AS
-- Position details
DECLARE @PositionX INT
DECLARE @PositionY INT
DECLARE @Orientation FLOAT

-- Level details
DECLARE @Maze VARCHAR(8000)
DECLARE @MazeWidth INT
DECLARE @MazeHeight INT

SELECT 
	@PositionX = PositionX,
	@PositionY = PositionY,
	@Orientation = Orientation,
	@Maze = Maze,
	@MazeWidth = MazeWidth,
	@MazeHeight = MazeHeight
FROM Games
INNER JOIN Levels
	ON Games.LevelName = Levels.LevelName
WHERE Games.UserName = USER_NAME()

IF(@@RowCount = 0)
BEGIN
	RAISERROR('You need to start a new game by calling spNewGame', 16, 1)
	RETURN
END


IF(dbo.fnIsExit(@Maze, @MazeWidth, @MazeHeight, @PositionX, @PositionY) = 1)
BEGIN
	EXEC spRender
	RETURN
END

DECLARE @NewX INT
DECLARE @NewY INT

SET @NewX = @PositionX
SET @NewY = @PositionY

IF(@Orientation = 0)
BEGIN
	SET @NewX = @PositionX + dbo.TILE_WIDTH()
END
ELSE IF(@Orientation = (PI() / 2)) 
BEGIN			
	SET @NewY = @PositionY + dbo.TILE_WIDTH()
END
ELSE IF(@Orientation = PI()) 
BEGIN			
	SET @NewX = @PositionX - dbo.TILE_WIDTH()
END
ELSE
BEGIN
	SET @NewY = @PositionY - dbo.TILE_WIDTH()
END

IF(dbo.fnIsSolid(@Maze, @MazeWidth, @MazeHeight, @NewX, @NewY) = 0)
BEGIN
	SET @PositionX = @NewX
	SET @PositionY = @NewY
END

SET NOCOUNT ON

UPDATE Games SET 
	PositionX = @PositionX, 
	PositionY = @PositionY 
WHERE UserName = USER_NAME()

SET NOCOUNT OFF

EXEC spRender
GO

CREATE PROCEDURE spLeft
AS
DECLARE @Orientation FLOAT

SELECT @Orientation = Orientation FROM Games WHERE UserName = USER_NAME()

IF(@Orientation >= (PI() / 2))
BEGIN
	SET @Orientation = @Orientation - (PI() / 2);
END
ELSE
BEGIN
	SET @Orientation = (PI() * 3) / 2;
END

SET NOCOUNT ON
UPDATE Games SET Orientation = @Orientation  WHERE UserName = USER_NAME()
SET NOCOUNT OFF

EXEC spRender
GO

CREATE PROCEDURE spNewGame
@LevelName VARCHAR(20) = 'Easy'
AS

DECLARE @Maze VARCHAR(8000)
DECLARE @MazeWidth INT
DECLARE @MazeHeight INT

SELECT 
	@Maze = Maze,
	@MazeWidth = MazeWidth,
	@MazeHeight = MazeHeight
FROM Levels WHERE LevelName = @LevelName

IF(@@RowCount = 0)
BEGIN
	RAISERROR('Level doesn''t exist', 16, 1)
	RETURN
END

DECLARE @PositionX INT
DECLARE @PositionY INT
DECLARE @Offset INT 

SET @Offset = CHARINDEX('S', @Maze) - 1

SET @PositionX = (@Offset % @MazeWidth * dbo.TILE_WIDTH()) + (dbo.TILE_WIDTH() / 2);
SET @PositionY = ((@Offset / @MazeWidth) * dbo.TILE_WIDTH()) + (dbo.TILE_WIDTH() / 2);

SET NOCOUNT ON

DELETE FROM Games WHERE UserName = USER_NAME()

INSERT INTO Games(UserName, LevelName, PositionX, PositionY, Orientation)
	SELECT USER_NAME(), @LevelName, @PositionX, @PositionY, 0

SET NOCOUNT OFF

EXEC spRender
GO

CREATE PROCEDURE spRender
AS
SET NOCOUNT ON 

DECLARE @Screen VARCHAR(8000)

-- Position details
DECLARE @PositionX INT
DECLARE @PositionY INT
DECLARE @Orientation FLOAT

-- Level details
DECLARE @Maze VARCHAR(8000)
DECLARE @MazeWidth INT
DECLARE @MazeHeight INT

SELECT 
	@PositionX = PositionX,
	@PositionY = PositionY,
	@Orientation = Orientation,
	@Maze = Maze,
	@MazeWidth = MazeWidth,
	@MazeHeight = MazeHeight
FROM Games
INNER JOIN Levels
	ON Games.LevelName = Levels.LevelName
WHERE Games.UserName = USER_NAME()

IF(@@RowCount = 0)
BEGIN
	RAISERROR('You need to start a new game by calling spNewGame', 16, 1)
	RETURN
END

IF(dbo.fnIsExit(@Maze, @MazeWidth, @MazeHeight, @PositionX, @PositionY) = 1)
BEGIN
	SELECT 'Congratulations you have finished the maze.'
	RETURN
END

EXEC spDrawWalls
	@PositionX = @PositionX,
	@PositionY = @PositionY,
	@Orientation = @Orientation,
	@Maze = @Maze,
	@MazeWidth = @MazeWidth,
	@MazeHeight = @MazeHeight,
	@Screen = @Screen OUT

DECLARE @Results TABLE
(
	Line VARCHAR(80)
)

DECLARE @i INT
SET @i = 0
WHILE(@i < dbo.SCREEN_HEIGHT())
BEGIN
	INSERT INTO @Results(Line)
		SELECT SUBSTRING(@Screen, dbo.SCREEN_WIDTH() * @i, dbo.SCREEN_WIDTH())

	SET @i = @i + 1
END

SELECT * FROM @Results

SET NOCOUNT OFF
GO

CREATE PROCEDURE spRight
AS
DECLARE @Orientation FLOAT

SELECT @Orientation = Orientation FROM Games WHERE UserName = USER_NAME()

IF(@Orientation <= PI())
BEGIN
	SET @Orientation = @Orientation + (PI() / 2);
END
ELSE
BEGIN
	SET @Orientation = 0;
END

SET NOCOUNT ON 
UPDATE Games SET Orientation = @Orientation  WHERE UserName = USER_NAME()
SET NOCOUNT OFF

EXEC spRender
GO

CREATE PROCEDURE spSetupIntersecionParams
@CameraX FLOAT,
@CameraY FLOAT,
@Angle FLOAT,
@Horizontal_x FLOAT OUT,
@Horizontal_y FLOAT OUT,
@Horizontal_step_x FLOAT OUT,
@Horizontal_step_y FLOAT OUT,
@Vertical_x FLOAT OUT,
@Vertical_y FLOAT OUT,
@Vertical_step_x FLOAT OUT,
@Vertical_step_y FLOAT OUT
AS

-----------------------------------------------------------------------
-- angle 0 to 89 degrees - parameter setup ...
-----------------------------------------------------------------------
IF(@Angle < (PI() / 2)) 
BEGIN			
	-------------------------------------------------------------------
	-- setup parameters for intersections with horizontal lines
	-------------------------------------------------------------------
	SET @Horizontal_step_x = (dbo.TILE_WIDTH() / TAN(@Angle))
	SET @Horizontal_step_y = dbo.TILE_WIDTH()
	
	SET @Horizontal_x = (@CameraX + ((dbo.TILE_WIDTH() / 2) / TAN(@Angle)))
	SET @Horizontal_y = @CameraY + (dbo.TILE_WIDTH() / 2)
	
	-------------------------------------------------------------------
	-- setup parameters for intersections with vertical lines
	-------------------------------------------------------------------
	SET @Vertical_step_x = dbo.TILE_WIDTH()
	SET @Vertical_step_y = dbo.TILE_WIDTH() * TAN(@Angle)
	
	SET @Vertical_x = @CameraX + (dbo.TILE_WIDTH() / 2)
	SET @Vertical_y = (@CameraY + ((dbo.TILE_WIDTH() / 2) * TAN(@Angle)))
END
-----------------------------------------------------------------------
-- angle 90 to 179 degrees - parameter setup ...
-----------------------------------------------------------------------
ELSE IF(@Angle < PI()) 
BEGIN				
	SET @Angle = @Angle - (PI() / 2)
	-------------------------------------------------------------------
	-- setup parameters for intersections with horizontal lines
	-------------------------------------------------------------------
	SET @Horizontal_step_x = -(dbo.TILE_WIDTH() * TAN(@Angle))
	SET @Horizontal_step_y = dbo.TILE_WIDTH()
	
	SET @Horizontal_x = (@CameraX - ((dbo.TILE_WIDTH() / 2) * TAN(@Angle)))
	SET @Horizontal_y = @CameraY + (dbo.TILE_WIDTH() / 2)
	
	-------------------------------------------------------------------
	-- setup parameters for intersections with vertical lines
	-------------------------------------------------------------------
	SET @Vertical_step_x = -dbo.TILE_WIDTH()
	SET @Vertical_step_y = (dbo.TILE_WIDTH() / TAN(@Angle))
	
	SET @Vertical_x = @CameraX - (dbo.TILE_WIDTH() / 2)
	SET @Vertical_y = (@CameraY + ((dbo.TILE_WIDTH() / 2) / TAN(@Angle)))
END
-----------------------------------------------------------------------
-- angle 180 to 259 degrees - parameter setup ...
-----------------------------------------------------------------------
ELSE IF(@angle < ((PI() * 3) / 2)) 
BEGIN
	SET @Angle = @Angle - PI()
			
	-------------------------------------------------------------------
	-- setup parameters for intersections with horizontal lines
	-------------------------------------------------------------------
	SET @Horizontal_step_x = - (dbo.TILE_WIDTH() / TAN(@Angle))
	SET @Horizontal_step_y = - dbo.TILE_WIDTH()
	
	SET @Horizontal_x = (@CameraX - ((dbo.TILE_WIDTH() / 2) / TAN(@Angle)))
	SET @Horizontal_y = @CameraY - (dbo.TILE_WIDTH() / 2)
	
	-------------------------------------------------------------------
	-- setup parameters for intersections with vertical lines
	-------------------------------------------------------------------
	SET @Vertical_step_x = -dbo.TILE_WIDTH()
	SET @Vertical_step_y = -(dbo.TILE_WIDTH() * TAN(@Angle))
	
	SET @Vertical_x = @CameraX - (dbo.TILE_WIDTH() / 2)
	SET @Vertical_y = (@CameraY - ((dbo.TILE_WIDTH() / 2) * TAN(@Angle)))
END
-----------------------------------------------------------------------
-- angle 270 to 359 degrees - parameter setup ...
-----------------------------------------------------------------------
ELSE
BEGIN
	SET @Angle = @Angle - (PI() * 3) / 2
	
	-------------------------------------------------------------------
	-- setup parameters for intersections with horizontal lines
	-------------------------------------------------------------------
	SET @Horizontal_step_x = (dbo.TILE_WIDTH() * TAN(@Angle))
	SET @Horizontal_step_y = -dbo.TILE_WIDTH()
	
	SET @Horizontal_x = (@CameraX + ((dbo.TILE_WIDTH() / 2) * TAN(@Angle)))
	SET @Horizontal_y = @CameraY - (dbo.TILE_WIDTH() / 2)
	
	-------------------------------------------------------------------
	-- setup parameters for intersections with vertical lines
	-------------------------------------------------------------------
	SET @Vertical_step_x = dbo.TILE_WIDTH()
	SET @Vertical_step_y = -(dbo.TILE_WIDTH() / TAN(@Angle))
	
	SET @Vertical_x = @CameraX + (dbo.TILE_WIDTH() / 2)
	SET @Vertical_y = (@CameraY - ((dbo.TILE_WIDTH() / 2) / TAN(@Angle)))
END

GO