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GameBoy Advance Programming

GameBoy Advance Programming. Tiles. Atari. 196?: As an engineering student at the University of Utah, Nolan Bushnell liked to sneak into the computer labs late at night to play computer games on the university's $7 million mainframes.

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GameBoy Advance Programming

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  1. GameBoy AdvanceProgramming Tiles

  2. Atari • 196?: As an engineering student at the University of Utah, Nolan Bushnell liked to sneak into the computer labs late at night to play computer games on the university's $7 million mainframes. • 1972: Bushnell founded Atari with $250 of his own money and another $250 from business partner Ted Dabney. They then created and commercialized the world's first commercial video game, Pong. Bushnell was 27 years old. • 1976: Warner Communications buys Atari from Bushnell for $28 million. • 1977: Atari introduces the Atari Video Computer System (VCS), later renamed the Atari 2600 • 1978: December - Atari announces the Atari 400 and 800 personal computers. • 1979: October - Atari begins shipping the Atari 400 and Atari 800 personal computers.

  3. Typical Atari 800 Screenshot

  4. Atari Graphics • Graphics and Text Modes • Display List • Customizable Fonts • Area in memory that described fonts (characters) • Area in memory that was what went on screen • Player/Missile Graphics

  5. GBA Tiles • Logical extension of the customizable character sets. Some of the terms used today are based on the historical derivation of the technology • (The logical extension of the player/missile graphics is sprites)

  6. Mode 3 Bitmaps Video Processing Circuitry Screen What color to make a certain pixel Video Memory

  7. Mode 4 Bitmaps Video Processing Circuitry Screen What color is that? What color number to make a certain pixel Video Memory Palette Memory

  8. Mode 0 Tilemaps Video Processing Circuitry Screen What tile number to make a group of pixels What does that tile look like? What color is that? Video Memory Tile Images (Character Blocks) Palette Memory

  9. Tiles On Screen 30 20

  10. Tiles & Tilemaps • Tile • 8x8 bitmap image • Treated like big pixels, as the building block of an image • 16 or 256 colors • 32 or 64 bytes • Tile Map • 2D array of tile indexes • Tile : Tilemap :: Pixel : Bitmap

  11. Tradeoff • 8 bpp = 256 colors • Lots of colors • All tiles share the same palette. • Tile images take more space • 4 bpp = 16 palettes of 16 colors apiece • Still have 256 colors • More constraints • More flexibility • Tile images smaller (i.e. can have more)

  12. Illustrations from Tonc

  13. GBA Tile Mode Features • Up to 4 tiled background layers • Up to 1024x1024 pixels each • Hardware scrolling • Maps can be larger than the screen • Hardware Parallax (optional) • Layers scroll at different speeds to simulate depth • Affine transformation (optional) • Rotation and scaling effects

  14. Steps to Tiles • Create tile images • Create screen image • Create a palette • Store tile images in a character block • Store screen image in one or more screen blocks • Store palette in palette memory area • Set image control buffer and Mode

  15. Steps to Tiles • Create tile images • Create screen image • Create a palette • Store tile images in a character block • Store screen image in one or more screen blocks • Store palette in palette memory area • Set image control buffer and Mode

  16. 1&2&3. gfx2gba • Usage gfx2gba -fsrc -t8 -mm file.bmp gfx2gba -fsrc -t8 -mm -c16 file.bmp • -fsrc means produce c source files • -t8 means 8 bit tiles • -m Optimize tile images (remove duplicates, flip, etc. • -c16 4bpp • file.bmp should be a 256 color (8bpp) image. • Add files to your project and extern them in your other files.

  17. 1&2&3. usenti

  18. 4,5&6. Video Memory CBB0 CBB1 CBB2 CBB3 CBB4 CBB5

  19. 4,5&6. Video Memory Tile Palette: 0x5000000 CBB0 CBB1 CBB2 CBB3 CBB4 CBB5

  20. 4,5&6. Video Memory Character Blocks 4 for tile images and maps 0x6000000 CBB0 CBB1 CBB2 CBB3 CBB4 CBB5 16kb 2kb

  21. 4,5&6. Video Memory Tile Palette: 0x5000000 Character Blocks 4 for tile images and maps 0x6000000 CBB0 CBB1 CBB2 CBB3 CBB4 CBB5 16kb 2kb

  22. 4,5&6. Video Memory Stop Here 0 0 0 0 0 0 2 3 0 2 1 1 3 4 4 4 4 1 2 3 4 CBB0 CBB1 CBB2 CBB3 CBB4 CBB5

  23. Tile Size • One 256 color tile has 8x8 8-bit indexes for a total of 64 bytes. One character block will hold 256 of these tile images. • One 16 color tile has 8x8 4-bit indexes for a total of 32 bytes. One character block will hold 512 of these images • Recall that there are 4 screen blocks but space for the tile map must be allocated.

  24. Do the Math • Suppose you had an image that was very complex?

  25. Can we tile this image?

  26. How big are things • 16 color tiles are 32 bytes apiece • 256 color tiles are 64 bytes apiece

  27. Can we tile this image? • Mode 3 video memory is 38400 shorts of 76800 bytes or 75KB • In tile mode at 8bpp (same as Mode 4) we will use 38400 bytes • In tile mode at 4 bpp we would use only 19200 bytes • EXCEPT!!!!

  28. Max Number of Tiles • In the tile map 10 bits are allocated to identify which tile goes in each position • 10 bits means we can only have 1024 unique tiles • We can actually make it look like more since tiles can be flipped or be colored differently • The screen is 20x30 tiles or 600 so we cannot tile an image that is > 1024 unique tiles!

  29. Mode & BG Specifics • Mode Backgrounds Rotation/Scaling • 0 0, 1, 2, 3 No • 1 0, 1, 2 Yes (only background 2) • 2 2, 3 Yes Background Resolution Rotation/Scaling • 0 512 x 512 No • 1 512 x 512 No • 2 128 to 1024 Yes • 3 128 to 1024 Yes

  30. Background Layers • 0 & 1 • Max Resolution 512x512 • Tile map of 16 bit numbers • 2 & 3 • Resolution from 128x128 to 1024x1024 • Rotation & Scaling • Tile map of 8 bit numbers

  31. Color • 256 color tiles • 8 bits per pixel • Tiles share one 256 color palette • 16 color tiles • 4 bits per pixel • Tiles use one of 16 palettes, 16 colors each • Note: Total palette is still 256 colors Incorrect: 256 color tiles being displayed as 16 color tiles Correct

  32. Tile Memory • Double the sprite memory compared with bitmap modes • Tile data video in video buffer • From 0x6000000 to 0x600FFFF • On 16k boundary (any of 4 spots) • Tile map also stored in video buffer • On 2k boundary (any of 32 spots) • Tile data and Tile map are in same space but normally would not overlap.

  33. Video Memory Tile Palette: 0x5000000 Character Blocks 4 for tile images and maps 0x6000000 CBB0 CBB1 CBB2 CBB3 CBB4 CBB5 16kb 2kb

  34. Tile Data and Tile Map • The tile map is stored in the same location as the video buffer (in the bitmap video modes), an array of numbers that point to the tile images. • In text backgrounds (0 and 1) the tile map is comprised of 16-bit numbers, while the rotation backgrounds (2 and 3) store 8-bit numbers in the tile map. • When working with tile-based modes, video memory is divided into 4 logical char base blocks, which are made up of 32 smaller screen base blocks, as shown on the next slide.

  35. Techniques • Tile images must start at the beginning of a character block • Tile maps must start at the beginning of a screen block • How do we determine the correct address • How do we do this in a C program?

  36. 4&5. Technique 1 • Calculate the address of each character block and each screen block and create a bunch of #defines for each one #define CHARACTERBLOCK0 0x6000000 #define CHARACTERBLOCK1 0x6004000 ... #define SCREENBLOCK0 0x6000000 #define SCREENBLOCK1 0x6000800 ...

  37. 4&5. Technique 2 • Write macros to calculate the addresses #define CHARBLOCK(n) \ (unsigned short *) (0x6000000+(n)*0x4000) #define SCREENBLOCK(n) \ (unsigned short *) (0x6000000+(n)*0x800)

  38. 4&5. Technique 3 • Let C do all the work! • Define structures: typedef struct { u16 tileimg[8192]; } charblock; typedef struct { u16 tilemap[1024]; } screenblock; • Define pointers charblock *charblockBase = (charblock *)0x6000000; screenblock *screenblockBase = (screenblock *)0x6000000;

  39. 4&5. Technique 3 Continued • Now you can directly access the block you want using array indexing!!!! for(i=0; i<PicTileLen; i++) { charblockBase[1].tileimg[i] = picTile[i]; } • What if i exceeds 8192???

  40. 6. Palette • No different than Mode 4!

  41. 7. Control Registers //background offset registers #define REG_BG0HOFS *(volatile unsigned short *)0x04000010 #define REG_BG1HOFS *(volatile unsigned short *)0x04000014 #define REG_BG2HOFS *(volatile unsigned short *)0x04000018 #define REG_BG3HOFS *(volatile unsigned short *)0x0400001C #define REG_BG0VOFS *(volatile unsigned short *)0x04000012 #define REG_BG1VOFS *(volatile unsigned short *)0x04000016 #define REG_BG2VOFS *(volatile unsigned short *)0x0400001A #define REG_BG3VOFS *(volatile unsigned short *)0x0400001E //background control registers #define REG_BG0CNT *(volatile unsigned short*)0x4000008 #define REG_BG1CNT *(volatile unsigned short*)0x400000A #define REG_BG2CNT *(volatile unsigned short*)0x400000C #define REG_BG3CNT *(volatile unsigned short*)0x400000E

  42. 7. BGxCNT 0F 0E 0D 0C 0B 0A 09 08 07 06 05 04 03 02 01 00 bits name description 0-1 Pr Priority. Determines drawing order of backgrounds. 2-3 CBB Character Base Block. Sets the charblock that serves as the base for character/tile indexing. Values: 0-3. 6 Mos Mosaic flag. Enables mosaic effect. 7 CM Color Mode. 16 colors (4bpp) if cleared; 256 colors (8bpp) if set. 8-12 SBB Screen Base Block. Sets the screenblock that serves as the base for screen-entry/map indexing. Values: 0-31. 13 Wr Affine Wrapping flag. If set, affine background wrap around at their edges. Has no effect on regular backgrounds as they wrap around by default. 14-15 Sz Background Size. Regular and affine backgrounds have different sizes available to them. 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 Sz Wr SBB CM M CBB Pr

  43. BGxCNT #defines //macros and bit constants for setting the background control register specifics #define SBB(num) num << 8 #define CBB(num) num << 2 #define COLOR256 1 << 7 // Cols x Row #define BG_SIZE0 0<<14 // 32 x 32 tiles #define BG_SIZE1 1<<14 // 64 x 32 #define BG_SIZE2 2<<14 // 32 x 64 #define BG_SIZE3 3<<14 // 64 x 64

  44. Tile Maps 0F 0E 0D 0C 0B 0A 09 08 07 06 05 04 03 02 01 00 bits name description 0-9 TID Tile ID 0-511 (Thus maximum number of tiles per background is 512 10 HF Horizontal flip if set 11 VF Vertical flip if set 12-15 PB Palette bank in 4bpp (16 color) mode. Ignored in 8bpp (256 color) mode 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 PB VF HF TID

  45. Moving on a Big Map

  46. SCREEN What's your model?Screen Moves? MAP

  47. SCREEN What's your model? MAP

  48. SCREEN What's your model? MAP

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