Tennis for Two, 1958, by William Higinbotham, Brookhaven National Lab

CSE 380 – Computer Game ProgrammingGraphics Device Management

What is a 2D game graphically speaking?

• Basically 2 things:– Texture rendering (images)– Text rendering

• Rendering textures & text is easy

• Efficiently managing the data of the game is not

DirectX

• Windows API for making games

• Microsoft says “The power of multimedia in Windows, DirectX gives you the best possible experience with graphics, sound, music, and 3-D animation.”

• API in MSDN:– http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_m/directx/directx9m.asp

DirectX ArchitectureWindows Win32 Application

Dir

ect3

D

XA

udio

…

Hardware: Audio, Video, Input, Storage …

HEL: Hardware Emulation Layer

HAL: Hardware Abstraction Layer

Softwareemulation

DirectX Devices

• Represent hardware

• Direct3D device is the graphics processor

• Graphics cards can render fast

• So, we call DirectX methods– they are implemented on the GPU

• What if you don’t have a GPU?– you can’t play

Challenge to PC game programmers

• Every gamer has a different machine

• Different graphics cards, which means:– different available screen resolutions– different available color models

• You want to reach a broad audience

• What’s the end result?– a headache– a lot of code devoted to dealing with these differences

What’s a color model?

• A format for storing color on the graphics card

• Many different formats

• Ex:– 32 ARGB

• 8 bits for Alpha

• 8 bits for Red

• 8 bits for Green

• 8 bits for Blue

What does a GPU have?

• A grid of pixels– match the current screen resolution– when we force to screen it ends up on monitor

• Memory for additional visual data– ex: textures

• Implementations of efficient graphics processing algorithms

Strategy for creating graphics devices

• Pick a common resolution, ex: 1024 X 768

• Pick a common color model, ex: 32 XRGB

• When the application starts:– check to make sure the player’s graphics card has these

capabilities– What if the player doesn’t have our desired format?

• have backup choices

• tell the player to come back when they have a better computer

Creating a D3D Graphics Device1. Make a Direct3D object (LPDIRECT3D9)

2. Get all the available GPU display modes (D3DDISPLAYMODE)

3. Pick one and use it to fill in the setup parameters (D3DPRESENT_PARAMETERS)

4. Use parameters to create a graphics device (LPDIRECT3DDEVICE9)

5. Use the graphics device to make a sprite handler (LPD3DXSPRITE)

– More on using this in a minute

Setup Direct3D Methods

• CreateDevice

• Direct3DCreate9

• EnumAdapterModes

• GetAdapterModeCount

• …

• These can tell us about the capabilities of the GPU

Making a Direct3D Object

• Let’s us make other stuff

LPDIRECT3D9 d3d;

…

d3d = Direct3DCreate9(D3D_SDK_VERSION);

• How about getting the available modes?– each color mode is numbered

– lets look for all modes in 1-1000 range (way overkill)

vector<D3DDISPLAYMODE*> *displayOptions = new vector<D3DDISPLAYMODE*>();

int adapterCounter = 1;

D3DFORMAT format;

while (adapterCounter < 1000)

{

format = D3DFORMAT(adapterCounter);

int numAdapters = d3d->GetAdapterModeCount(

D3DADAPTER_DEFAULT, format);

D3DDISPLAYMODE *displayModes =

new D3DDISPLAYMODE[numAdapters];

for (int i = 0; i < numAdapters; i++)

{

d3d->EnumAdapterModes(D3DADAPTER_DEFAULT,

format, i, &displayModes[i]);

displayOptions->push_back(&displayModes[i]);

}

adapterCounter++;

}

Getting all display modes

Does it have our desired format?

bool hasMode = false;

vector<D3DDISPLAYMODE*>::iterator iterator;

iterator = displayOptions->begin();

while ((iterator != displayOptions->end()) && !hasMode)

{ D3DDISPLAYMODE *testMode = (*iterator);

if ((testMode->Format == DEFAULT_COLOR_MODE)

&& (testMode->Width == DEFAULT_SCREEN_WIDTH)

&& (testMode->Height == DEFAULT_SCREEN_HEIGHT))

hasMode = true;

iterator++;

}

• Now we can make our graphics device & sprite handler

LPDIRECT3DDEVICE9 graphicsDevice;

D3DPRESENT_PARAMETERS presentParameters;

LPD3DXSPRITE spriteHandler;

…

ZeroMemory(&presentParameters,sizeof(presentParameters));

presentParameters.Windowed = true;

presentParameters.SwapEffect = D3DSWAPEFFECT_DISCARD;

presentParameters.hDeviceWindow = hWnd;

presentParameters.BackBufferFormat = formatToUse;

presentParameters.BackBufferWidth = screenWidthToUse;

presentParameters.BackBufferHeight = screenHeightToUse;

HRESULT result = d3d->CreateDevice(D3DADAPTER_DEFAULT,

D3DDEVTYPE_HAL, presentParameters.hDeviceWindow,

D3DCREATE_HARDWARE_VERTEXPROCESSING,

&presentParameters,

&graphicsDevice);

result = D3DXCreateSprite(graphicsDevice, &spriteHandler);

So what?

• LPD3DXSPRITE can draw 2D images

• LPDIRECT3DDEVICE9 can draw text

• To draw text we need a LPD3DXFONT

Making a font objectLPD3DXFONT textFont;

…

HRESULT result = D3DXCreateFont(

graphicsDevice,

20,

0,

FW_BOLD,

0,

FALSE,

DEFAULT_CHARSET,

OUT_DEFAULT_PRECIS,

DEFAULT_QUALITY,

DEFAULT_PITCH | FF_MODERN,

TEXT(""),

&textFont );

Oh, and we need to load images

• For this, we need a color key. What’s that?– color ignored while loading an image

• Why would this be useful?– game shapes aren’t all rectangular

• Important methods:– D3DXGetImageInfoFromFile– D3DXCreateTextureFromFileEx

• Let’s use them:

D3DXIMAGE_INFO info;

HRESULT result = D3DXGetImageInfoFromFile(fileName, &info);

if (result == S_OK)

{ D3DCOLOR colorKey = D3DCOLOR_XRGB(96, 128, 224);

LPDIRECT3DTEXTURE9 textureToLoad;

result = D3DXCreateTextureFromFileEx(

graphicsDevice, fileName,

info.Width, info.Height,

1, D3DPOOL_DEFAULT,

D3DFMT_UNKNOWN, D3DPOOL_DEFAULT,

texture,

D3DX_DEFAULT,

D3DX_DEFAULT,

colorKey,

&info,

NULL,

&textureToLoad );

Now we want to draw them

• There is a bit of overhead in rendering a single texture

• Solution?– pool that overhead– called batch texture rendering

Each Frame

1. clear screen

2. reserve the GPU for rendering

3. start sprite batch

4. render all textures

5. render text

6. end sprite batch

7. unreserve the GPU

8. force the GPU to the screen

Rendering a frame

graphicsDevice->Clear(0, NULL, D3DCLEAR_TARGET,

D3DCOLOR_XRGB(96, 96, 96), 1.0f, 0);

graphicsDevice->BeginScene();

spriteHandler->Begin(D3DXSPRITE_ALPHABLEND);

result = spriteHandler->Draw( texture,

imageRect, NULL, &position, alphaColor);

result = textFont->DrawText ( spriteHandler, L"Render this Text", -1, &textRect,

DT_LEFT, D3DCOLOR_XRGB(96, 96, 96) );

spriteHandler->End();

graphicsDevice->EndScene();

graphicsDevice->Present(NULL, NULL, NULL, NULL);

Did you get all that?

• Believe me, you’ll get used to it

Texture Management• Skilled game programmers recycle images

• Think of a tiled game background– the same images duplicated many times

• Efficient Solution: texture manager

• When you load a level:– load one of each needed image into a level texture

manager– for rendering, refer to image indices in texture manager

What might a texture manager do?

• Store all textures

• Store all names of texture files & paths

map<wstring, LPDIRECT3DTEXTURE9> textures;

• Provide methods for:– loading, accessing, reloading, etc.

We might also want a string table

vector<wstring> stringTable;

• Why?– ints take up less memory than wstrings

• So how do we use it?– when initializing game items use image index– game items store stringTable index to represent texture– when time to draw, ask stringTable for string at index– swap string for texture in texture manager

We’ll use 2 TextureManagers

• One for the GUI

• One for the Level

• Why use 2?

Windowed vs Fullscreen mode

• Windowed:– Can minimize, maximize, hit “x” to close, etc.– Share GPU– Share all resources

• Fullscreen– you get the resources– how do we get out?

• Game control (exit game for example)

• ALT-TAB

The Evil ALT-TAB

• When in Full-Screen mode:

– What happens when someone ALT-TABS?• We lose the graphics device

• How do we get it back?

• Someone needs to ALT-TAB back

– How can we deal with this?• Check to see if our game has the GPU every single frame

HRESULT result = graphicsDevice->TestCooperativeLevel();

if (SUCCEEDED(result))

{

// RENDER THE GAME HERE

}

else if (result == D3DERR_DEVICELOST)

{

// SOME OTHER APPLICATION HAS THE GPU, MAYBE

// AN ALT-TAB, WE JUST HAVE TO KEEP TRYING TO

// GET IT BACK

Sleep(100);

}

else if (result == D3DERR_DEVICENOTRESET)

{

// YAY! WE GOT THE GPU BACK, MAYBE SOMEONE ALT-TABBED BACK

// RESET THE GRAPHICS CARD AND RELOAD ALL THE TEXTURES

if (FAILED(graphicsDevice->Reset(&presentParameters)))

// RELOAD ALL IMAGES

}