Sonic Rush BAC Format
From Sonic Retro
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Revision as of 09:38, 7 July 2022 by Ccawley2011 (talk | contribs) (Created page with "{{HistoricalArticle|equivalent=Sonic Rush/Technical information|source=https://web.archive.org/web/20140118114435/http://jaquadro.homedns.org/~stream/Sonic_rush_bac.txt}} <pre...")
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This historical hacking document is preserved here for archival purposes. It has not been revised since its original writing and may be outdated. For an SCHG-equivalent document, see Sonic Rush/Technical information. Original source: https://web.archive.org/web/20140118114435/http://jaquadro.homedns.org/~stream/Sonic_rush_bac.txt |
Sonic Rush BAC Format By Justin Aquadro (Retriever II) This document is incomplete and is not 100% accurate Please send additions, corrections to [email protected] Last Updated: 7/19/06 @ 2:49AM EDT Byte Order: Little Endian ------------------------------------------------------------------------------------------------ BLOCK HIERARCHY +-------+ +-------+ |BLOCK 2|+ . . .|BLOCK 1|+ +-------+| +-------+| +--|----+ +-------+ | | +-------+ |BLOCK 3| +-------+ | +---------------+---------------+ | | | +-------+ +-------+ +-------+ |BLOCK 4| |BLOCK 5| |BLOCK 6|+ +-------+ +-------+ +-------+| +-------+ ------------------------------------------------------------------------------------------------ Header Block ADDR SIZE DESCRIPTION 0x0000 4 Header: BAC\x0A 0x0004 4u Address Block 2 0x0008 4u Address Block 3 0x000C 4u Address Block 4 0x0010 4u Address Block 5 0x0014 4u Address Block 6 0x0018 4u Address Block 1? (Constant: 0x1C) ------------------------------------------------------------------------------------------------ Block 1 (Global Sprite Data? / Animation Sets?) ADDR SIZE DESCRIPTION 0x0000 4u Size of block 0x0004 2u Number Block 2s, Number SubBlock 1s in Block 1 0x0006 2 Unknown (defaults?) 0x0008 2 Unknown (defaults?) 0x000A 2 Unknown (defaults?) 0x000C 2 Unknown (defaults?) 0x000E 2 Unknown (defaults?) 0x0010 2 Unknown (defaults?) 0x0012 2 Unknown (defaults?) 0x0014 2 Unknown (-1) 0x0016 2 Unknown (always 0?) 0x0018 2 Unknown (always 0?) 0x001A 2 Unknown (always 0?) | | SubBlock 1 (Animation Set?) | 0x0000 2 Unknown | 0x0002 2 Unknown | 0x0004 2 Unknown | 0x0006 2 Unknown | 0x0008 2 Unknown | 0x000A 2 Unknown | 0x000E 2 Unknown | 0x000C 2 Unknown | 0x0010 2 Unknown (always 0?) | 0x0012 2 Unknown (always 0?) ------------------------------------------------------------------------------------------------ Block 2 (Animation Set Mappings?) ADDR SIZE DESCRIPTION 0x0000 4u Size of block | | SubBlock 1 (Single Mapping?) | 0x0000 4u Offset into Block 3 | 0x0004 4u Unknown (always 0?) ------------------------------------------------------------------------------------------------ Block 3 (Animation Frames / Set) ADDR SIZE DESCRIPTION 0x0000 4u Size of block | | SubBlock 1 (Single Frame)* | 0x0000 2 ID 01: Frame Offsets | 0x0002 2 Length of Frame Offsets SSB, plus ID | | | | SubSubBlock 1 (Frame Offsets) | | 0x0000 4u Offset into Block 4 (Frame Data) | | | 0x0004 2 ID 02: Image Parts | 0x0006 2 Length of Image Part SubSubBlocks, plus ID | | | | SubSubBlock 2 (Image Parts) | | 0x0000 4u Offset into Block 6 (Image Data) | | 0x0004 4u Data Size Block 6 / 0x20? | | | 0x0008 2 ID 03: Palettes | 0x000A 2 Length of Palette SubSubBlocks, plus ID | | | | SubSubBlock 3 (Palettes) | | 0x0000 4u Offset into Block 5 (Palette Data) | | 0x0004 4u Number colors in palette? | | | 0x000E 2 ID 07: Unknown Purpose | 0x000C 2 Length of Unknown Purpose SubSubBlocks, plus ID | | | | SubSubBlock 4 (Alternate Bounadaries / Collision Masks? Usually not present) | | 0x0000 4 Index (for external identification?) | | 0x0004 2 Alternate Boundary X-Coordinate Left Edge? | | 0x0006 2 Alternate Boundary Y-Coordinate Top Edge? | | 0x0008 2 Alternate Boundary X-Coordinate Right Edge? | | 0x000A 2 Alternate Boundary Y-Coordinate Bottom Edge? | | | 0x0010 2 ID 00: Animation Info | 0x0012 2 Length of Animation Info SubSubBlocks, plus ID | | | | SubSubBlock 5 (Animation Info) | | 0x0000 2 Number frames in Set | | 0x0002 2 Frame Index | | 0x0004 4 Duration of frame in time units? | 0x0004 2 ID 04: Resting/default frame? 0x0006 2 Length of resting frame data, plus ID? 0x0008 4u Offset to one of the frame SubBlocks, usually the first (resting frame?) * There is no gaurentee that any ID/length pair and its corresponding SSB will be present in a given frame. ------------------------------------------------------------------------------------------------ Block 4 (Frame Assembly) ADDR SIZE DESCRIPTION 0x0000 4u Size of block | | SubBlock 1 (Single Frame Assembly) | 0x0000 4u Number image parts in frame (parts specified in animation frame) | 0x0004 2 X-Coordinate Left Edge | 0x0006 2 Y-Coordinate Top Edge | 0x0008 2 X-Coordinate Right Edge | 0x000A 2 Y-Coordinate Bottom Edge | 0x000C 2 Hot Spot X-Coordinate | 0x000E 2 Hot Spot Y-Coordinate | | | | SubSubBlock 1 (Image Part Coordinate Offsets) | | 0x0000 1 Y-Coordinate Offset from Top Edge | | 0x0001 1 Unknown | | 0x0002 1 X-Coordinate Offset from Left Edge | | 0x0003 1 Unknown | | 0x0004 2 Unknown | | 0x0006 2 Unknown ------------------------------------------------------------------------------------------------ Block 5 (Palettes) ADDR SIZE DESCRIPTION 0x0000 4u Size of block | | SubBlock 1 (Single Palette) | 0x0000 1 Unknown (type?) | 0x0001 3 Size of palette | | | | SubSubBlock 1 (Palette Entry) | | 0x0000 2 Palette Entry, 4bpp ------------------------------------------------------------------------------------------------ Block 6 (Image Data) ADDR SIZE DESCRIPTION 0x0000 4u Size of block | | SubBlock 1 (Single Image Part) | 0x0000 1 Compression? (0x00=Uncompressed, 0x10=LZSS) | 0x0001 3 Size of data region | | | | SubSubBlock 1 (Pixel Pair) | | 0x0000 1 Pixel Pairs | | | 0x0004-7 1-4 Terminator (-1) (Padding? 1-4 bytes?) ------------------------------------------------------------------------------------------------ NOTES: To save data, some images with larger regions of empty space are broken apart into multiple images, and combined after. These are the frames that have extra long Block 4 sub-blocks. All frames use a Hot Spot from which the dimentions of the frame are calculated. Image parts are laid down according to pixel offsets from the top and left edges of the frame. It would appear that image part dimentions are calculated by filling in to the right and bottom until the other frame edges are encountered or other allocated space is encountered. This could be problematic for some placements, but tile constraints could make this possible. ------------------------------------------------------------------------------------------------ "UNUSUAL" FILES ac_sonic.bac (No palette/data B3:SSBs) dm_stdm_jpn.bac (Missing some data B3:SSBs) ------------------------------------------------------------------------------------------------ CREDIT: Contributer Identifications Techokami Compression byte in Image Data