★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 6 Rotating scroll screen
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VDP2 User's Manual / Chapter 6 Rotating Scroll Screen
● Rotational read of frame buffer
- Rotational reading of the frame buffer is performed using the screen screen start coordinates (Xst, Yst), screen screen vertical coordinate increments (DXst, DYst), and screen screen horizontal coordinate increments (DX, DY) of rotation parameter A.
If you display the image specified by rotation parameter A on the rotation scroll screen, you can rotate the entire sprite and the rotation scroll screen in the same way.
You can rotate the entire sprite and the rotation scroll screen separately by displaying the image specified by rotation parameter B on the rotation scroll screen.- The display coordinate value of the frame buffer is calculated from the display coordinates of the left end of the line calculated for each line from the screen screen start coordinates and the screen screen vertical coordinate increment, and the horizontal coordinate increment of that line.
At this time, from the coordinate range of the frame buffer, the display coordinate value at the left end of the line is a sign + integer part 10 bits + fraction part 9 bits, for a total of 20 bits, and the horizontal coordinate increment is sign + integer part 2 bits + fraction part 9 bits. It is calculated by truncating the bits so that there are a total of 12 bits.- In order to perform a rotation read of the framebuffer using rotation parameter A, the TV mode of VDP1 must be set to rotation 16 or rotation 8. For more information, see VDP1 User's Manual.
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★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 6 Rotating scroll screen
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