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Diffstat (limited to 'apps/plugins/xracer/README')
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diff --git a/apps/plugins/xracer/README b/apps/plugins/xracer/README new file mode 100644 index 0000000..8b6312c --- /dev/null +++ b/apps/plugins/xracer/README @@ -0,0 +1,79 @@ +This file contains some quick notes about this plugin. +====================================================== + +Some useful links: +------------------ + +<http://codeincomplete.com/projects/racer/> - a very good tutorial on building a similar game in Javascript + +<http://www.extentofthejam.com/pseudo/> - excellent page on pseudo-3d + +Terminology: +------------ + +In the code, a "fixed-point" number is one that has a nonzero number of fractional bits. +When dealing with these numbers, you must be careful to convert all operands to fixed-point, and use the correct function/macro to replace the operators. +In the code, I've tried to make all fixed-point numbers of type 'long.' +An "integer" is a number with zero fractional bits. + +(NOTE: I'm not sure if this "proper" terminology) + +Code structure: +--------------- + +generator.c: random map generator + +graphics.c: this is where almost all of the rendering takes place + +main.c: main loop + +sprite.c: static sprite data (offsets, dimensions) + +util.c miscellaneous functions, also contains FOV calculation code + +Proposed map formats: +--------------------- + +There will be two map formats: one that can be compiled into the executable ("Internal format"), and one that can be loaded from a file ("Interchange format"). + +Internal format: +---------------- + +This format is represented as a series of struct road_section's. + +struct road_section { + uchar type; + uint32 len; + int slope; + long curve; // <<< this is fixed-point with 8 fracbits +}; + +'type' can be any of the following: + 0: constant segment - all 3 parameters used + 1: up-hill - an up hill is added. actual length is len + 2*slope due to enters and exits + 2: down-hill - a down hill is added. actual length is len + 2*slope due to enters and exits + +Endianness is platform-dependent in the Internal format. + +Interchange format: +------------------- + +NOTE: all numbers are BIG-ENDIAN unless otherwise specified! + +This format is essentially the Internal format serialized into a file, but with some minor differences. + +File extension: .xrm + +Current format version number: 0x0000 + +- File header - 8 bytes + - 0x00-0x04: 'XMaP' + - 0x05-0x06: version number (see above) + - 0x07-0x08: 0xFF padding +- Data blocks - 15 bytes each (corresponds to the "sections" of the Internal format) + - 0x00 : type + - 0x01-0x04: length + - 0x05-0x08: slope (signed two's complement) + - 0x09-0x0C: curve (signed two's complement, fixed-point with 8 fractional bits) + - 0x0D-0x0E: CRC16-CCITT of data from 0x0-0xC + - 0x0F : CRC high byte XOR CRC low byte |