From Sonic Retro
|SCHG: Sonic Jam|
This is the Sonic Community Hacking Guide for Sonic Jam.
(In alphabetical order; if you are a contributor and have worked on a specific part of the guide, feel free to note that.)
Pieces of the guide not big enough for their own page should be left here.
Fixed Point Numbers
A fixed point number is how fractional numbers were handled in most games in this era, as opposed to floating point numbers.
In Sonic Jam, a fixed point number consists of two words. The upper word is the integer part, while the lower word is the fractional part, out of 65536; there's essentially a decimal point between the two words. For example, 1.0 would be written $0001 0000, whereas 0.5 would be written $0000 8000, 0.25 would be $0000 4000, and so on.
Negatives are handled just like integers. This means that -1.0 would be written $FFFF 0000, whereas -0.5 would be $FFFF 8000, -0.25 would be $FFFF C000, and so on.
Angles in this game appear to always be words, where 0 degrees is $0000, 90 degrees is $4000, 180 degrees is $8000, and so on.