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Chapter 6 Rotating scroll screen

The rotary scroll screen has two sets of parameter tables called “Rotation parameter A” and “Rotation parameter B”, and the screens based on each parameter table can be displayed simultaneously. The two sets of parameters can be stored in the VRAM as a corresponding parameter table in addition to being stored in the VRAM as a rotation parameter table.
Rotation parameters have two sets, rotation parameter A and rotation parameter B, and each is stored in a table. RBG0 can display one screen specified by rotation parameter A or rotation parameter B or two screens specified by rotation parameter A and rotation parameter B at the same time. RBG1 is a screen specified by rotation parameter B. Can only display. Table 6.1 shows the relationship between the rotation scroll screen and rotation parameters.

Table 6.1 Rotating scroll screen
Screen Single display Relation with rotation parameters
RBG0 Yes One screen specified by either rotation parameter A or B,
or rotation parameter A or B Two specified screens can be displayed at the same time
RBG1 Impossible (RBG0 must also be displayed
) 		Display the screen specified by the rotation parameter B

Rotation parameter A and rotation parameter B can each have a coefficient table, and various data can be displayed by reading the coefficient data for each line or dot. ∙ You can also use the rotation parameter A to rotate the frame buffer for sprites.

■ 6.1 Rotating scroll coordinate calculation

The display screen of the rotary scroll screen rotates and converts the viewpoint and screen screen (TV screen) (including translation) based on the center point, and the line of sight passing through the converted screen screen from the converted viewpoint. A collection of points that intersect a fixed scroll map. Figure 6.1 shows how to display the rotating scroll screen.

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