If you Google it (along with "Street Fighter") you get the following text (or slight variations) a BUNCH of times:
What in the crap does that even mean?Progressive Hit Frame System - This programming technique enables a more realistic "Hit Frame" or "Collision Box" detection. The area in which a player makes contact with their opponent is precisely calculated and based on a single frame of animation.
Then you get someone's 'explanation' of it later on in the results:
Still very unclear. So, what? did they take one frame decide "this is the frame we're basing our collisions on" and they draw a bunch of boxes along a realistic path of the fist/foot and then play these in time? The word progressive kind of makes me think it's something along those lines. Could it be any more vague. Someone suggested the Eternal Challenge mook has more details. I have the Japanese version which I can't read...This new combat element enables more realistic collision boxes and hit frames. Basically, each contact point has been streamlined to one frame of animation.
In what world does "streamline [something] into a single frame of animation" make sense for hitboxes? Are we even still talking about hitboxes? How is this better than the way it's done in every other game?
Someone suggested to me that this means they use a pixel by pixel comparison of sprites to determine a collision. I really can't swallow that. It requires more storage (you need a colored version of every sprite to identify the hitting parts of the sprite), it's slower than just checking if a couple of rectangles overlap AND there's just too strong a gut feeling that it's just WRONG. I've seen Chun's B+HP hit rediculously. I've seen parts of sprites overlap that didn't cause an impact which definitely should have it was pixel perfect.
Can anyone help answer my burning questions?