I posted this query elsewhere, but as part of a different topic -- so it perhaps got a bit lost...
I'm wondering if there were any good technical reason for Microsphere Wheelie's use of the teabag/mesh graphical style for its backgrounds. Personally, I thought the effect was great. Regardless, it definitely isn't a style that's common on the Spectrum, so I'd appreciate any relevant technical perspective.
It seems it was likely for performance reasons. The game uses RLD/RRD to scroll the screen, and the graphical style means that only every second row has to be scrolled.
djnzx48 wrote: ↑Wed Jun 19, 2019 11:51 pm
It seems it was likely for performance reasons. The game uses RLD/RRD to scroll the screen, and the graphical style means that only every second row has to be scrolled.
Thanks. I don't really understand the technical component of that but I do get the principle -- less to shift, right? But, are we sure that's the reason here? There are plenty of games that scrolled beautifully that *didn't* use this graphical style... so perhaps it's just a product of its age?
You could probably alter the game to use more solid graphics, and change the code to run over every line on the screen. But it would likely run twice as slowly.
For some reason they've put the scrolling code into contended memory, so the instruction combination used incurs up to 34 T-states of contention delays for every byte scrolled. And RLD/RRD aren't very efficient instructions in the first place. So yes, I would say it's partly because it was written in 1983 when there wasn't as much of a focus on optimising games to run quickly.
I wonder if the game would run significantly faster on a +2A/+3 for that reason.
