Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual page 71

AGB Programming Manual
Operations Used in OBJ Rotation/Scaling Processing
1. Specify the rotation/scaling parameter number to be applied in OBJ
Attribute 1 of the OAM.
2. The image-processing circuit sums the increases in the x direction (dx,
dy) in relation to the center of rotation (OBJ field center), which serves
as reference point, to calculate the x-direction coordinates.
3. When the line is advanced, the increases in the y-direction (dmx, dmy)
in relation to the reference point, are summed to calculate the
coordinate of the starting point for rendering the next line. The
processing in step 2) above, is then performed.
Rotation/Scaling Parameters
Specifies the direction of character data reference in OBJ rotation/scaling
processing.
The values set for PA, PB, PC, and PD are signed, fixed-point numbers
(8-bit fractional portion, 7-bit integer portion, 1-bit sign, for a total of 16 bits).
These 4 parameters are used together as a single group, which can be
placed in any of 32 areas in OAM.
PA
PB
PC
PD
©1999 - 2001 Nintendo of America Inc.
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
dx: distance moved in x direction along same line
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
dmx: distance moved in x direction along next line
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
dy: distance moved in y direction along same line
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
dmy: distance moved in y direction along next line
71
Rendering Functions
D.C.N. AGB-06-0001-002B4