Creating a Level Loader

1
Creating a Level Loader

• Bryan Duggan
• Hugh McAtamney

2
What is a level loader

• Loads up the geometry and textures for each level
• We now have enough information to create a Dalek
  World level loader
• Vectors
• Matrices
• The rendering pipeline
• Vertex buffers
• Texturing
• File I/O using stdio
• OO Framework

3
New framework classes
4
DrawableEntity

• An interface in Java terms
• Does nothing, but has an API with virtual member
  functions
• setup
• update
• draw
• cleanup
• From now on, anything that draws will extend
  this class
• All drawable things in the game have a standard
  API

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BoundableEntity

• Anything that has lower and upper bounds extends
  this class
• We can use it later for things like bounding box
  collision detection

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World

• Extends DrawableEntity and BoundableEntity
• Encapsulates Dalek World and everything in it
• Draws the SkyBox, floor
• Contains the camera
• Has Vectors of
• Internal walls
• Daleks
• Ammunition

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Wall

• Extends DrawableEntity and BoundableEntity
• Draws an internal wall

8
Hang on..

• I thought a vector was like a point in 3d space???

9
C Vectors

• Consider the following C function
• int add(int a, int b)
• return a b
• This works for ints, but if we want to use
  floats, we have to write another function
• float add(float a, float b)
• return a b
• This is bad. What if we could pass the type as a
  parameter

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C Vectors

• To get around this problem, C introduces
  templates
• A template is like passing a type as a parameter.
  Example
• template lttypename tgt
• t add(t a, t b)
• return a b

t is a type. The compiler will create a function
for any type that the program uses
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To use a template

• You simply call the method as normal!
• ints
• int a, b
• a 10 b 20
• printf("a d b d a b d\n", a, b,
  add(a, b))
• floats
• float c, d
• c 60.8 d 39.2
• printf("c f d f c d f\n", c, d,
  add(c, d))
• Even strings!
• string f ("Hello"), g (" World")
• string h add(f, g)
• cout ltlt h

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The STL

• In fact C now has a huge library of template
  based classes that can simplify the writing of
  your programs

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C Vector

• Is like a dynamic array
• We do not have to worry about the size of the
  array
• We can just add and remove elements as necessary
• The vector class keeps track of memory use and
  allocates more or less memory as necessary

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To use a vector
Without the .h!

• include ltvectorgt
• void main()
• vectorltintgt ages
• ages.push_back(21)
• ages.push_back(24)
• ages.push_back(33)
• ages.push_back(27)

Our vector will hold ints
Add elements to the end of the vector
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Vector iteration
The size of the vector

• for (int i 0 i lt ages.size() i )
• printf("Age of student d is d\n", i, agesi)
• You can also use
• vectorltintgtiterator it
• it ages.begin()
• i 0
• while (it ! ages.end())
• printf("Age of student d is d\n", i, it )
• it
• i

Get the ith element
Create an iterator
Make the iterator point to the 1st element
The contents of the iterator is the element
Increment the iterator To make it point to the
next element
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World class

• Uses vectors to keep references to
• walls
• daleks
• projectiles
• E.g.
• stdvectorltWallgt _walls
• Wall wall
• wall new Wall()
• wall-gtsetBounds(x0, y0, z0, x1, y1, z1)
• _walls.push_back(wall)
• for(int i 0 i lt _walls.size() i)
• _wallsi-gtsetup(device)

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Loading assets

• In a game an asset is
• An audio file
• A texture
• A mesh (collection of vertices)
• We only want to load each asset once
• For example
• If our game had 5000 walls
• And each wall loaded a 1Mb texture
• Then we would be using 5Mb, just to store the
  same texture over and over again!

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The solution is

• The singleton design pattern
• A singleton is
• A class that only allows you to create one
  instance of it.
• The singleton takes care of lazy loading assets
  (loading the asset only once and on demand).

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To implement a singleton in C

• Make the constructor private
• private
• AssetLoader()
• Create a static pointer to an instance of the
  class. This will be the single instance of the
  class created
• static AssetLoader _theInstance
• Create a static accessor member function that
  constructs the instance if it does not already
  exist
• AssetLoader AssetLoaderinstance()
• if (AssetLoader_theInstance NULL)
• AssetLoader_theInstance new AssetLoader
• return AssetLoader_theInstance

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Finally

• In C, the static member will not be created
  until its assigned a value, so you must include
• AssetLoader AssetLoader_theInstance NULL
• At some point in your code

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Lazy loading

• Now you can lazy load the assets in a similar
  manner. E.g.
• IDirect3DTexture9 AssetLoadergetTexture(const
  char fileName, IDirect3DDevice9 device)
• IDirect3DTexture9 texture NULL
• texture _texturesfileName
• if (texture NULL)
• D3DXCreateTextureFromFile(device, fileName,
  texture)
• _texturesfileName texture
• return texture