I have not followed this thread, but I assume you are talking from the point of a zipless/glitchless run.
The rules I defined in
http://tasvideos.org/userfiles/user/Bisqwit (refined from the post at
http://tasvideos.org/forum/p/365009#365009) for a glitchless run of
Mega Man, original, was to categorically ban any manifestation of player-caused movement of Mega Man
faster than he could normally run or walk. Zips that cause him to momentarily move
slower are still fine, an example being a collision check instantly zeroing his subpixel component. This includes the example in your post above.
The most arguable application of this rule involves ladders. Ladders can instantly zip Mega Man both horizontally and vertically to align with the ladder, and this happens trivially in casual play even. When such movement speed exceeds Mega Man’s jumping speed (as measured by compared to what happens if up/down is
not pressed at that moment), it is banned.
The underlying guideline behind my rules is to ban any abuse of tradeoffs between the game’s perfect/correct behavior and code size/performance, whether intentional (as in “<developer> Yes, I know it’s not
exactly correct, but vast majority of players will never notice anything wrong, and fixing it would increase chances we run out of budget for money, ROM space, or production schedule”) or unintentional (as in “<developer> Oops! The game is not supposed to do that.”).
But what about this?
You can't see it, but here, Mega Man pops up from 94.08 to 94.00--3% of a pixel. Seems like pretty standard behavior for the collision code, if you ask me. But before you answer, look at this:
A lot of jumps in this run end up looking like this. You clip inside the block by less than half a pixel, then get pushed out on the next frame. Should this be considered a zip? Redoing large portions of my run to be slower just so I can avoid this particular edge case seems absurd. Especially when you consider realtime runs; how can a judge tell if I popped up 3% of a pixel on a particular jump, or if I landed "normally?"
My proposed definition is this: if the floor/wall ejects you less than one whole pixel, the collision code is behaving as normal, and you are not zipping. This definition allows me to get good subpixel precision in my jumps, while banning the intended exploit: jamming your body into the ceiling and blasting off at inane speeds. It also provides reasonable criteria for RTA judges to look for in any ambiguous runs.
Regardless of whatever consensus is reached here, I've decided to jump for an extra frame in the particular scene that I showed, to circumvent the issue. I'm waiting for that Item 2 to spin up, so it doesn't really matter. I just wanted to clear this up before moving on.
