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Old 13 October 2019, 23:03   #4
dodke
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Join Date: Feb 2018
Location: London / UK
Posts: 73
1. Is the bob static? Try moving the bob on the screen and you should see what the issue is. For example if you have your bob at the top left corner at 0,0 then the 16 bit wide bob will be in the first 2 bytes of the bitplane. But if you'd like to draw the bob one pixel to the right (so at 1,0) it won't be in the first 2 bytes anymore. The last pixel will be in the 3rd byte of that bitplane. And then you need to pad to words as that's what blitter uses so 4 bytes / 32 pixels.

2. You don't need it for bobs. But for example if you are drawing a rectangle of any size you'd probably want to use these registers. The blitter will only copy words / 16 pixels but you can set these registers to fine tune the left (first word of a line) and right (last) edges of the rectangle to be at any pixel position.
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