SOURCE 2006

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SOURCE 2006
Game Programming Optimization

• Presentation by Luke Arntson
• ArntsonL_at_cwu.edu

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Optimization Research

• How important is optimization in games?
• Optimization is the most essential part of
  coding when it comes to game development. Coders
  must always take into consideration the
  optimization of their solutions to ensure
  full-speed games.
• What types of optimization will we cover?
• There are many ways to properly optimize
  programs, including games. In this presentation,
  we will cover many ways of solving the same
  problems using optimization as key. The beauty of
  programming is the ability to be creative with
  the solutions, and finding new ways to approach
  old problems.

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What Games Are We Going To Cover?

• Tetris the classic puzzle
• block game
• Bullet Dodger a vertical
• space shooter
• Death Bomberman a clone of
• the original Bomberman

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Creating and Optimizing Tetris

• First, start with the layout
• The most prevalent type of layout for the Tetris
  piece is a 4x4 array. This array is used to tell
  the game where the Tetris blocks will be. By
  simplifying the Tetris piece itself, we can
  simplify the problem. I have implemented a system
  using the Tetris block coordinates in the 4x4
  array, rather than the array itself.
• Next, let us look at rotations
• So now that we have determined the Tetris pieces
  can be created with coordinates, let us observe
  how we can apply rotations to these pieces.

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Layout of Tetris Pieces

• With permission of Phil Hassey, code from FTetris
• philhassey FTetris _at_ http//www.imitatio
  npickles.org/ftetris/
• 1. Box shape
• 2. Z shape
• 3. T shape
• my Tetris
  example
• Note Numbers represent distance from
  top left corner
• Numbers are also in order Left, Top,
  Right, and Bottom
• 1. Box shape 1.
  (0,1), (0,0), (1,0), (1,1)
• 2. Z shape 2.
  (0,0), (1,0), (2,1), (1,1)
• 3. T shape 3.
  (0,0), (1,0), (2,0), (1,1)
• See how much code was saved? Not only has this
  decreased the code amount significantly, but has
  also lead a path of optimization.

2. (0,0,0,0), (1,1,0,0),
(0,1,1,0), (0,0,0,0),
1. (0,0,0,0),
(0,1,1,0), (0,1,1,0),
(0,0,0,0),
3.(0,0,0,0), (1,1,1,0),
(0,1,0,0), (0,0,0,0),
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Visual Example Of Phil Hasseys Code

• Here is a visual representation of how the 4x4
  array is being drawn in Fractal Tetris by Phil
  Hassey.

• ? Let us pretend we are building a Tetris piece,
  and the piece is made of four blocks

• ? Each block is represented as a 1 or a 0 in the
  4x4 array

• ? We can now observe the array and watch how the
  1s and 0s fill the grid

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Visual Example Of Coordinates in Tetris

• Let use now examine the code given for
  coordinates of the piece, rather than a 4x4 array.

• ? Let us pretend we are building a Tetris piece,
  and the piece is made of four blocks

• ? Each block has (x,y) coordinates on a 4x4 grid

• ? We can now match the coordinates given with the
  code (0,0), (1,0), (2,0), (1,1)

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How Do We Represent Rotations?

• First, what is a set of rotations?
• A set of rotations can be defined as a list of
  pieces. So using (X,Y) coordinates, we can
  define the following
• Z Piece
• 1st.(0,0), (1,0), (2,1), (1,1) 2nd.(0,1),
  (1,0), (1,1), (0,2)
• T Shape Piece
• 1st.(0,0), (1,0), (2,0), (1,1) 2nd.(0,1),
  (1,0), (1,1), (1,2)
• 3rd.(0,1), (1,0), (2,1), (1,1) 4th.(0,1),
  (0,0), (1,1), (0,2)
• 7 Shape Piece
• 1st.(0,0), (1,0), (1,1), (1,2) 2nd.(0,1),
  (2,0), (2,1), (1,1)
• 3rd.(0,1), (0,0), (1,2), (0,2) 4th.(0,0),
  (1,0), (2,0), (0,1)

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Optimizing The Rotation

• Now that we know our rotation, lets look at how
  we can optimize
• Notice that different pieces have a different
  number of rotations. For example, the large block
  shape only has one rotation, and the Z shape has
  two rotations, as where the T shape has four
  rotations. Now we can break these pieces into
  sub-groups based on the number of rotations.
• Break our shapes into sub-groups, and apply
  rotation
• After each sub-group is found, rotation is
  simple. In high level code, if the shape is in
  the current state, increment or decrement
  depending on which function is called. The number
  of states to rotate is determined by the
  sub-group given.

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Bullet Dodger How To Optimize All Those Bullets?

• Code must be simple yet effective
• For games such as Bullet Dodger, the speed of
  the frames are vital. If the game had been
  written on a console such as the Gameboy Advance,
  limitations with the number of cycles would
  always be a factor of programming.
• Collision checking only potentials
• It would be pointless to check every single
  bullet to every single enemy or player unless
  there was a potential of harm. By using a
  grid-collision system, collision checking can be
  brought down significantly while still
  maintaining a solid collision checking system.

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Simple Code With Effective Results

• Bullet patterns in commercial games
• All space shooting games, old and new, rely on
  the concept of bullet patterns. In an older game
  such as Space Invaders, bullets simply flew down
  in a straight line towards the player. Later
  games such as Gradius used simple angle
  calculations to shoot bullets at the player.
• Moving the bullets in a linear path
• Applying simple math skills, it is easy to find
  the calculation for bullets. The simplest way to
  sum this up is by imagining there is a velocity
  vector to each bullet. The vector consists of an
  angle, and a vector length. By using the
  following code every frame, bullets can achieve a
  smooth travel across the playing field
• Bullet X Coordinate cos(vector.angle)
  vector.length
• Bullet Y Coordinate sin(vector.angle)
  vector.length
• This simple calculation is used in Bullet
  Dodger to allow for a very nice looking effect
  not only for the bullets fired, but also for the
  simple particle engine used when there is a
  collision.

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Simple Yet Effective Bullet Patterns

• Applying the unit circle to a bullet spread
• Currently using Pi/2 (-Pi/8 lt x lt Pi/8)

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Collision Detection Using Grid-collision

• Lets split our screen into separate grid
  sections. Notice how the player ship and enemies
  are only in a few boxes, not ALL boxes. This is
  the idea we will implement to our grid-collision

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Observing Where Objects Can Collide In Our Grid

• Areas of collision
• Now observe the red areas, see that the only
  places these objects can be hit is within these
  red sections. So ONLY do tedious collision
  detection in these boxes areas, saving a vast
  amount of processor time.

15
Death Bomberman World Manager and Optimization

• Managing the world is difficult
• However, eliminating the need for objects to be
  self-sufficient allows for much cleaner code. If
  an object tells the world its desired movement or
  action, the world can then dictate whether or not
  the object is allowed to do so. This can be
  applied to many different games, and has been
  applied to many coding schemes used by major
  companies.
• How world management optimizes games
• By eliminating unnecessary checks such as
  wall-collision, game code can run at full speed
  while the world takes care of all special cases.
  For example when bombs explode, they create a
  fire burst. Instead of each fire burst checking
  for an object to burn, the world manager tells
  the object to burn, and the fire burst to die
  out.

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Applying to Death Bomberman

• Utilize the manager to make the world function
• By applying the world manager effectively, each
  object in the world will behave accordingly.
  Bombs will be placed correctly, and maps will
  know which items to destroy and which to leave
  intact.

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Questions?

• For more information on this presentation,
  feel free to visit my website at
• http//source.eyeforcode.com
• or email me at
• ArntsonL_at_cwu.edu