When you perform an edgebug, all of your vertical velocity drops to 0, while horizontal velocity stays the same.It's not possible to perform an edgebug without any horizontal velocity.Attempting to perform an edgebug with a lower framerate increases the success rate of triggering the glitch.It doesn't matter if you are ducked or not when doing an edgebug, both is going to work fine. The game never knows if you were on the ground or not, never applying the falldamage. When you perform an edgebug, you start in mid-air and end in mid-air in one movement frame, while sliding off of an edge happens in-between. Such checks are done at the end of movement frames. The engine applies the fall damage if the check if the player is on ground succeeds. Especially easy to do on stairs or other broad edges. Edgebug is a glitch in the engine that allows you to fall down a long distance without taking any damage and/or dying, by hitting the exact edge/brush of a certain block (in the case of Portal 2 and some of its mods, allows you to keep a button activated when there is nothing on it).
