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How FA/GC affects Frame Data

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Preface - Hanzo was asking me about how Sindel's Scream punishing sweep may change depending upon FA and GC. So I am making this post to explain this in detail.

There is a common misconception that the presence of FA or GC determines whether a character can punish certain moves on block every round. The reasoning itself is based upon the fact that certain combos are only possible if a character has GC. However, the claim is false, but I will present an example to explain why this belief is so prevalent.


Required background information:
  • If P1 and P2 input the same attack at the same time and P1 hits P2, then P1 is said to have Frame Advantage (FA) and P2 is said to have the ability to Glitch Cancel (GC).
  • FA and GC are determined for each character randomly at the start of each round.
  • If a player has GC then they will recover 1f earlier on hit and block then they normally would with FA.
  • Each character's shadow in the background moves 1f earlier then the character's sprite.
  • Depending on which platform is used, the game may have a differing amount of lag. For this post I will use MAME 0.129 (2f lag).
Consider the following example of Kabal attempting to punish the Male Ninja's uppercut on block with Spin. This is a just frame punish.

FA: Kabal, GC: HSmoke
18000

GC: Kabal, FA: HSmoke
18001

Comparing the two, we can see that while the sprite animation is constant, the GC character's moves are coming out 1f slower than the FA character's.
Furthermore, GC characters with recover 1f faster on block because the FA character's attack is hitting on time.

Both of these results combined show that FA and GC do not affect whether a block punish is possible. It also illuminates the reason why people believe that certain just-frame punishes are impossible depending on advantage. It is because they must be done at different times.
 
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