Nintendo 1504166 Programming Manual - Page 71
Operations Used in OBJ Rotation/Scaling Processing, Rotation/Scaling Parameters
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AGB Programming Manual Rendering Functions 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. 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 PA 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 PB 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 PC 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 PD dmy: distance moved in y direction along next line ©1999 - 2001 Nintendo of America Inc. 71 D.C.N. AGB-06-0001-002B4