Sprite Animation

1
Sprite Animation

• Lecture 5
• Abdennour El Rhalibi

2
Architectural Overview of DirectDraw

• DirectDraw enables a much higher level of
  efficiency and speed in graphics-intensive
  applications for Windows than is possible with
  GDI, while maintaining device independence.
• DirectDraw provides tools to perform such key
  tasks as
• Manipulating multiple display surfaces
• Accessing the video memory directly
• Page flipping
• Back buffering
• Managing the palette
• Clipping
• The DirectDraw component provides services
  through COM-based interfaces. In the most recent
  iteration, these interfaces are IDirectDraw7,
  IDirectDrawSurface7, IDirectDrawPalette,
  IDirectDrawClipper, and IDirectDrawVideoPort.

3
The Interfaces of DirectDraw
4
Using Interface Together

• Create DirectDraw object
• Retrieve a IDirectDraw7 interface
• Create at least a primary surface using
  IDirectDrawSurface
• Create a palette using IDrectDrawPalette
• Initialize palette
• Attach it to the surface
• Create a single clipper and size it.
• Draw on the primary surface.

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DirectDraw Clipper
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Creating a DirectDraw Object

• LPDIRECTDRAW lpdd NULL
• if (FAILED(DirectDrawCreate(NULL, lpdd, NULL))
• // error
• DirectDrawCreate parameters
• lpGUID GUID of the display driver that we want
  use.
• Usually, NULL the default hardware.
• lpdd Pointer to a pointer receiving IDirectDraw
  interface pointer.
• pUnkOuter advanced.. Just NULL

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Getting an Interface Lift

• LPDIRECTDRAW lpdd NULL
• LPDIRECTDRAW lpdd7 NULL
• if (FAILED(DirectDrawCreate(NULL, lpdd, NULL)))
  
• // error
• if (FAILED(lpdd-gtQueryInterface(IID_IDirectDraw7,
  (LPVOID )lpdd7)))
• // error
• lpdd-gtRelease( )
• lpdd NULL
• // use lpdd7

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Cooperating with Windows - 1

• Two modes
• Full-screen mode
• like an old DOS program
• Entire screen is for DirectDraw
• No GDI can be used
• Easy to handle
• Windowed mode
• Game is one of the clients on Windows Desktop
• Rather hard to control
• Still have full access to 2D and 3D acceleration

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Cooperating with Windows - 2

• IDirectDraw7SetCooperativeLevel( )
• HRESULT SetCooperativeLevel(HWND hWnd, DWORD
  dwFlags)
• Control Flags
• For full screen
• DDSCL_ALLOWMODEX 320x200, 320x240, 320x400
• DDSCL_ALLOWREBOOT CtrlAltDel rebooting
• DDSCL_EXCLUSIVE
• DDSCL_FULLSCREEN
• For Windowed Mode
• DDSCL_NORMAL

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Cooperating with Windows - 3

• Example
• Game_Init( ) and Game_Shutdown( ).
• int Game_Init(void parms NULL, int num_parms
  0)
• if (FAILED(DirectDrawCreate(NULL, lpdd,
  NULL)))
• if (FAILED(lpdd-gtQueryInterface(IID_IDirectDr
  aw4, )
• lpdd4-gtSetCooperativeLevel(main_window_handle
  , DDSCL_NORMAL)
• int Game_Shutdown(void parms NULL, )
• if (lpdd4)
• lpdd4-gtRelease( )
• lpdd4 NULL

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Getting into the Mode of Things

• SetDisplayMode(DWORD dwWidth,
• DWORD dwHeight,
• DWORD dwBPP, // bits per pixel 8, 16,
  24, 32
• DWORD dwRefreshRate, // 0 for default
• DWORD dwFlags) // extra flags (advanced)
  0 for default
• // 640x480 with 256 colors
• lpdd4-gtSetDisplayMode(640, 480, 8, 0, 0)
• // 800x600 with 16bit colors
• lpdd4-gtSetDisplayMode(800, 600, 16, 0, 0)

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Steps for 256 Color Mode

• Create palette 256 PALETTENTRY
• Create IDirectDrawPalette object
• Attach the palette object to a drawing surface.
• (Optional) You can change the palette entries.

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Palette Data Structure

• PALETTEENTRY palette256
• // Black at palette0
• palette0.peRed 0
• palette0.peGreen 0
• palette0.peBlue 0
• palette0.peFlags PC_NOCOLLAPSE //
  preventing optimization by DirectX
• 
  .
• // White at palette255
• palette255.peRed 255
• palette255.peGreen 255
• palette255.peBlue 255
• palette255.peFlags PC_NOCOLLAPSE
• .

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IDirectDrawPalette

• Using IDirectDraw7CreatePalette( )
• LPDIRECTDRAWPALETTE lpddpal NULL // palette
  interface
• if (FAILED(lpdd4-gtCreatePalette(DDPCAPS_8BIT
  DDPCAPS_INITIALIZE DDPCAPS_ALLOW256,
• palette, lpddpal, NULL)))
• // error

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Building a Display Surface
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Sprite animation
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New goodies

• perform full-screen animation using 3 frames of
  animation
• make the crow from example look like its flying
• Use a timer to control rate at which frames are
  displayed

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What is needed

• add the following libraries
• ddraw.lib
• winmm.lib
• Need 3 images
• Middle.bmp
• Up.bmp
• Down.bmp

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The Timer

• class is CTimer, with constructor Ctimer()
• file is Timer.h
• int m_nStartTime records start time
• virtual void start() starts the timer
• virtual int time() returns time in ms
• BOOL elapsed(int start, int interval)
• returns TRUE if interval ms have elapsed since
  start
• returns FALSE otherwise

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The Timer class
class CTimer //game timer class protected
int m_nStartTime //time that timer was started
public CTimer() //constructor virtual
void start() //start the timer virtual int
time() //return the time in ms //has
interval ms elapsed since start? BOOL
elapsed(int start,int interval)
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windows API function
include "timer.h" CTimerCTimer()
m_nStartTime(0) void CTimerstart()
m_nStartTimetimeGetTime() int
CTimertime() return timeGetTime()-m_nStartTime
int CTimerelapsed(int start, int
interval) //has interval elapsed from start?
int current_timetime() if(current_timegtstart
interval) start current_time return TRUE
else return FALSE
elapsed_time ?
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Main.cpp
CBmpFileReader frame0,frame1,frame2 int
current_frame0 //current frame of
animation CTimer Timer //game timer BOOL
LoadImages() //load graphics from files to
surfaces if(!frame0.load("Right.bmp"))return
FALSE frame0.draw(lpPrimary) //draw to
primary surface if(!frame0.setpalette(lpPrimaryP
alette))return FALSE if(!frame0.setpalette(lpSe
condaryPalette))return FALSE
if(!frame1.load("Middle.bmp"))return FALSE
if(!frame2.load("Left.bmp"))return FALSE
return TRUE
all 3 images use same palette
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Example1 vs Example2
while(TRUE) if(PeekMessage(msg,NULL,0,0,PM_N
OREMOVE)) if(!GetMessage(msg,NULL,0,0))ret
urn msg.wParam TranslateMessage(msg)
DispatchMessage(msg) else
if(!ActiveApp)WaitMessage()
while(TRUE) if(PeekMessage(msg,NULL,0,0,PM_N
OREMOVE)) if(!GetMessage(msg,NULL,0,0))ret
urn msg.wParam TranslateMessage(msg)
DispatchMessage(msg) else
if(ActiveApp) ProcessFrame() else
WaitMessage() //WinMain
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ProcessFrame()
BOOL ProcessFrame() //process a frame of
animation ComposeFrame() //compose a frame in
secondary surface return PageFlip() //flip
video memory surfaces //ProcessFrame
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BOOL ComposeFrame() static int
last_timeTimer.time() //Check that
current_frame stay in the range
if(current_framelt0)current_frame0
if(current_framegt3)current_frame3 //show a
frame switch(current_frame) case 0
frame0.draw(lpSecondary) break case 1
frame1.draw(lpSecondary) break case 2
frame2.draw(lpSecondary) break case 3
frame1.draw(lpSecondary) break //go to
next frame if(Timer.elapsed(last_time,100))
if(current_framegt4)current_frame0 return
TRUE
Why 4?
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Oops
BOOL ProcessFrame() ComposeFrame() return
PageFlip() //flip video memory surfaces
switch(current_frame) case 0
frame0.draw(lpSecondary) break case 1
frame1.draw(lpSecondary) break case 2
frame2.draw(lpSecondary) break case 3
frame1.draw(lpSecondary) break
How does the page get to lpPrimay?
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Sprite Animation
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New Goodies

• What is a sprite
• how to set up a sprite file
• what is blitting
• transparent blitting in DirectDraw
• separating an image from its properties
• how to load draw multi-frame sprites
• What happens if you try to draw outside the screen

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sprite animation

• a sprite is a small piece of artwork that moves
  across the screen
• sprite animation is animating a sprite
• sprites can have several frames of animation

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blitting

• drawing a sprite on a background
• DirectDraw permits transparent blitting
• designate one or more palette positions as
  transparent
• draw sprites with holes in them so we can see the
  background

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A Sprite file
multiple sprites in a single file allow the
artist to compare frames for consistency. All
artwork must be drawn with the same palette.
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The Palette

• Sprites.bmp uses same palette as Bckgnd.bmp
• all of the artwork in a game must use the same
  palette
• background color for Sprites.bmp is magenta
  (255,0,255)
• important thing is not color but palette position
  must use same palette position to indicate
  transparent pixels

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Messing up the transparency color
If the artwork is inconsistent with the program,
the sprite will be drawn with a block around it.
The same art tool used on two different
platforms may reverse the palettes on their
images.
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transparent palette position

• doesnt matter what color you put in transparent
  palette position since pixels are never drawn
• best to use a color that isnt used elsewhere in
  the game so that the artist/tool doesnt use that
  palette position, expecting it to be drawn

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The bounding box

• The smallest rectangle that can fit around the
  sprite
• in Sprites.bmp, all frames for a multi-frame
  sprite have same height/width
• have to measure each sprite frame
• for 640?480, top left pixel is 0, bottom right
  pixel is (639, 479)
• bounding box
• easier to identify top left bottom right
• easier to see if you mess up!

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This sprite is too large
If the sprite is too large, it may mess up a
neighboring sprite. if sprite is too small,
the sprite will be clipped along one or more
edges.
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reading sprites from a file
CBmpFileReader
base class reads an image from a file. Derived
class reads a sprite (a rectangle) from a sprite
file the sprite file has multiple frames of
an image!
CBmpSpriteFileReader
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draw first difference
class CBmpSpriteFileReader public
CBmpFileReader public //reuse everything in
base except draw() BOOL draw(LPDIRECTDRAWSURFA
CE surface, int width,int ht,int x,int y)
//draw sprite found in Sbmp.cpp similar to
CBmpFileReaderdraw, except src is set to
point y rows up from the bottom of the file, and
x pixels across. bmp files are store
upside-down src m_cImage
((m_BMPFileInfo.biHeight-1-y)m_BMPFileInfo.biWidt
hx)
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draw second difference
BOOL draw(LPDIRECTDRAWSURFACE surface, int
width ,int ht, int x,int y) //draw
sprite Second difference for loop in draw only
moves ht rows of data, and each row has width
width, for(int i0 ilt ht i) //for each
row memcpy(dest,src,width) //copy
destddsd.lPitch src-m_BMPFileInfo.biWidth
//next row
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BOOL CBmpFileReaderdraw (LPDIRECTDRAWSURFACE
surface) DDSURFACEDESC ddsd //direct draw
surface descriptor BYTE dest,src
//destination and source pointers int
src_width //width of source memset(ddsd,0,sizeof
(DDSURFACEDESC)) ddsd.dwSizesizeof(ddsd) if(F
AILED(surface-gtLock(NULL,ddsd,DDLOCK_WAIT,NULL)))
return FALSE dest(BYTE)ddsd.lpSurface
//destination srcm_cImage
((m_BMPFileInfo.biHeight-1)m_BMPFileInfo.biWidth)
//trim bmp if too wide if(m_BMPFileInfo.biWi
dthgtddsd.lPitch)src_widthddsd.lPitch else
src_widthm_BMPFileInfo.biWidth //move data to
surface for(int i0 iltm_BMPFileInfo.biHeight
i) memcpy(dest,src,src_width)
destddsd.lPitch src-src_width
surface-gtUnlock(NULL) return TRUE //draw
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class CBaseSprite //simplest sprite
protected LPDIRECTDRAWSURFACE m_lpDDImage
//sprite image int m_nFrameCount //how many
frames used in sprite int m_nWidth,m_nHeight
//dimensions of sprite images void
CreateSurfaces() //create surfaces public
CBaseSprite(int frames,int w,int h)
//constructor CBaseSprite() //destructor
BOOL load(CBmpSpriteFileReader image,int frame,
int x,int y) virtual void draw(int
frame,int x,int y, LPDIRECTDRAWSURFACE
destination) //draw sprite void Release()
//release when game is over BOOL Restore()
//restore if user de-iconifies int
frame_count() //return number of frames int
height() //return height int width()
//return width
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The constructor/destructor
extern LPDIRECTDRAW lpDirectDrawObject
CBaseSpriteCBaseSprite (int frames, int
width, int height) m_nFrameCount(frames),
m_nWidth(width), m_nHeight(height)
m_lpDDImagenew LPDIRECTDRAWSURFACEframes
for(int i0 iltframes i) m_lpDDImageiNULL
//create surfaces for sprite images
CreateSurfaces() CBaseSpriteCBaseSprite ()
deletem_lpDDImage
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The plane example is 1 frame!This example is
from Main.cpp
BOOL LoadImages() //load graphics from files to
surfaces if(!background.load("bckgnd.bmp"))return
FALSE background.draw(lpBackground) //set
palettes in all surfaces if(!background.setpalet
te(lpPrimaryPalette))return FALSE
if(!background.setpalette(lpSecondaryPalette))retu
rn FALSE //load the plane sprite
if(!g_cSpriteImages.load("sprites.bmp"))return
FALSE planespritenew CBaseSprite(1,121,72)
if(!LoadPlaneSprite())return FALSE //load plane
images return TRUE
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void CBaseSpriteCreateSurfaces()
DDSURFACEDESC ddsd //direct draw surface
descriptor ddsd.dwSizesizeof(ddsd) //required
field ddsd.dwFlagsDDSD_CAPSDDSD_HEIGHTDDSD_WI
DTH ddsd.ddsCaps.dwCapsDDSCAPS_OFFSCREENPLAIN
//offscreen ddsd.dwHeightm_nHeight
ddsd.dwWidthm_nWidth DDCOLORKEY ddck
//direct draw color descriptor
ddck.dwColorSpaceLowValue ddck.dwColorSpaceHighVa
lue TRANSPARENT_COLOR //set in Defines.h
for(int i0 iltm_nFrameCount i) //for each
frame if(FAILED(lpDirectDrawObject-gt
CreateSurface(ddsd,(m_lpDDImagei),NULL))) m_
lpDDImageiNULL //set the transparent
color m_lpDDImagei-gtSetColorKey(DDCKEY_SRCB
LT,ddck)
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The Object class

• Each object in the game is describe by Cobject
• the class encapsulates everything about the
  object, including
• its physical characteristics
• its image
• header file Objects.h

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include "bsprite.h" class CObject //class for
a moving object private int m_nX,m_nY
//current location int m_nXspeed,m_nYspeed
//current speed int m_nLastXMoveTime //last
time the object moved CBaseSprite m_pSprite
//pointer to sprite public CObject()
void draw(LPDIRECTDRAWSURFACE surface) void
create(int x,int y,int xspeed,int yspeed,
CBaseSprite sprite) //create instance void
accelerate(int xdelta,int ydelta0) //change
speed void move() //make a move depending on
time and speed
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The draw in CObject
// The object knows where to draw itself void
CObjectdraw(LPDIRECTDRAWSURFACE
surface) m_pSprite-gtdraw(0,m_nX,m_nY,surface)
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The constructor
extern CTimer Timer CObjectCObject()
m_nXm_nYm_nXspeedm_nYspeed0
m_pSpriteNULL m_nLastXMoveTime0
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Object creation
void CObjectcreate(int x,int y,int xspeed,int
yspeed, CBaseSprite
sprite) m_nLastXMoveTime0 //time m_nXx
m_nYy //location m_nXspeedxspeed
m_nYspeedyspeed //speed m_pSpritesprite
//image
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Speeding up the object
void CObjectaccelerate(int xdelta,int ydelta)
m_nXspeedxdelta m_nYspeedydelta
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void CObjectmove() //move object const int
XSCALE8 //to scale back horizontal motion
const int MARGIN100 //margin on outside of
page int xdelta //change in position int
timeTimer.time() //current time //horizontal
motion int tfactortime-m_nLastXMoveTime
//time since last move xdelta(m_nXspeedtfactor
)/XSCALE //x distance moved m_nXxdelta //x
motion if(xdeltam_nXspeed0)
m_nLastXMoveTimetime //wrap left
if(m_nXlt-MARGIN)m_nXSCREEN_WIDTHMARGIN
//wrap right if(m_nXgtSCREEN_WIDTHMARGIN)m_nX-M
ARGIN
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ComposeFrame()
BOOL ComposeFrame() //compose a frame of
animation //draw background
lpSecondary-gtBltFast(0,0,lpBackground,NULL,
DDBLTFAST_NOCOLORKEYDDBLTFAST_WAIT) //move
objects plane.move() //draw objects
plane.draw(lpSecondary) return TRUE
//ComposeFrame