Impact knockback

[tehtmi]

Some missiles produce explosions upon impact. The impact no longer does any damage, but it still causes knockback based on an otherwise-unused damage roll.

Probably, impact should cause no knockback, as the explosion will cause knockback as well. This has two main effects:

1) Explosive weapons have much higher knockback because they get both impact and explosion knockback.

2) Explosion damage is affected by the target's position after being knocked back by impact. For high damage weapons like the BFG 9000 and Acid Spitter, this can severely reduce (or even eliminate) damage done to the main target. For the player, this can cause Fireangel to trigger even if the player was directly hit. This effect very noticeable in AoMC.