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  • Joined: 21 Apr 2019
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SG-1000 Flicky scrolling
Post Posted: Wed May 01, 2019 11:17 pm
How does the SG-1000 version of Flicky pull off smooth scrolling?
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  • Joined: 19 Oct 2012
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Post Posted: Thu May 02, 2019 12:27 pm
boye wrote
How does the SG-1000 version of Flicky pull off smooth scrolling?

I'd have to look at how this runs in an emulator, but it very likely uses the same technique I used (and many before me) in my Alex Kidd port on the TI994A, which uses the same VDP as the SG-1000. You basically upload 8 pattern tables to VRAM, with each page after the first representing a 1-pixel shifted version of the character table. Important to know is that this limits the available number of characters quite a bit, since you have a character definition entry for each unique pair of characters on the screen (you basically scroll the left-most character into the rightmost one).

You can see it in action here:

I pre-calculate all of this stuff using a small C program on my mac, and upload the precalculated tables at load time. It is also possible to do this on the computer itself, but that greatly increases load times (in favor of requiring less storage on disk/cart).
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