Animating the Appearance of Sprites

1
Animating the Appearance of Sprites Creating
Backgrounds
2
Incorporate Frame Animation Into Sprite Animation

• Rely on a series of bitmap images to represent
  more than one appearance for the sprite
• Store a series of frame images vertically/horizont
  ally in a single image
• Then only draw the current frame as part of an
  image
• Additional information for animated sprite
• Total number of frames
• Current frame
• Frame delay
• Frame trigger //count down delay and indicate
  when its time to move to the next frame

3
Changes in Bitmap class

• void DrawPart(HDC hDC, int x, int y, int xPart,
  int yPart, int wPart, int hPart, BOOL bTrans,
  COLORREF crTransColor) // a New method in the
  Bitmap class
• if (m_hBitmap ! NULL)
• // Create a memory device context for the
  bitmap
• HDC hMemDC CreateCompatibleDC(hDC)
• // Select the bitmap into the device
  context
• HBITMAP hOldBitmap (HBITMAP)SelectObject(h
  MemDC, m_hBitmap)
• // Draw the bitmap to the destination
  device context
• if (bTrans)
• TransparentBlt(hDC, x, y, wPart, hPart,
  hMemDC, xPart, yPart, wPart, hPart,
• crTransColor)
• else
• BitBlt(hDC, x, y, wPart, hPart, hMemDC,
  xPart, yPart, SRCCOPY)
• // Restore and delete the memory device
  context
• SelectObject(hMemDC, hOldBitmap)
• DeleteDC(hMemDC)

4
Changes in Sprite Class

• //turns a normal sprite into an animated sprite
  by setting its
• number of frames
• void SpriteSetNumFrames(int iNumFrames)
• // Set the number of frames
• m_iNumFrames iNumFrames
• // Recalculate the position
• RECT rect GetPosition()
• rect.bottom rect.top ((rect.bottom -
  rect.top) / iNumFrames)
• SetPosition(rect)

5
Changes in Sprite Class Cont.

• //updates the sprites current animation frame
• void SpriteUpdateFrame()
• if ((m_iFrameDelay gt 0) (--m_iFrameTrigger
  lt 0))
• // Reset the frame trigger
• m_iFrameTrigger m_iFrameDelay
• // Increment the frame
• if (m_iCurFrame gt m_iNumFrames)
• m_iCurFrame 0

6
Changes in Sprite Class Cont.

• // draw the sprite differently depending on
  whther or not it is an animated sprite
• void SpriteDraw(HDC hDC)
• // Draw the sprite if it isn't hidden
• if (m_pBitmap ! NULL !m_bHidden)
• // Draw the appropriate frame, if necessary
• if (m_iNumFrames 1)
• m_pBitmap-gtDraw(hDC, m_rcPosition.left,
• m_rcPosition.top, TRUE)
• else
• m_pBitmap-gtDrawPart(hDC,
  m_rcPosition.left, m_rcPosition.top, 0,
  m_iCurFrame
• GetHeight(), GetWidth(), GetHeight(),
  TRUE)

7
Types of Game Backgrounds

• Solid backgrounds
• Consist only of a solid color
• Image backgrounds
• Use a bitmap image to represent the background
• Animated backgrounds
• Changes its appearance over time
• Write custom code to update and draw the
  background
• Scrolling backgrounds
• Involves an image or set of graphical objects
  capable of being shifted or scrolled around on
  the screen

8
A Basic Background Class

• class Background
• protected
• // Member Variables
• int m_iWidth, m_iHeight
• COLORREF m_crColor
• Bitmap m_pBitmap
• public
• // Constructor(s)/Destructor
• Background(int iWidth, int iHeight,
  COLORREF crColor)
• Background(Bitmap pBitmap)
• virtual Background()
• // General Methods
• virtual void Update()
• virtual void Draw(HDC hDC)
• // Accessor Methods
• int GetWidth() return m_iWidth
• int GetHeight() return m_iHeight

9
A Derived Animated Background Class

• class StarryBackground Background
• protected
• // Member Variables
• int m_iNumStars
• int m_iTwinkleDelay
• POINT m_ptStars100
• COLORREF m_crStarColors100
• public
• // Constructor(s)/Destructor
• StarryBackground(int iWidth, int iHeight,
  int iNumStars 100,
• int iTwinkleDelay 50)
• virtual StarryBackground()
• // General Methods
• virtual void Update()
• virtual void Draw(HDC hDC)