What is the best way to do melee weapon collision?

[Keytotruth]

@kennyrosenyc;310528

Watch the 3rd Person tutorial on you tube (the series by Unreal Engine). There’s a whole section on ‘punching’. All you have to do is put a collision box around the part that does damage and then use Blueprints to make it do damage.

Thing is that with that approach other problems arise. You can put a box around the object, but then I won’t be getting the impact normal and other useful things. Plus, a box is a kinda crappy way to detect collision. I’d rather use some sort of more “automatic” way.

@RhythmScript;310535

It depends: do you need information about the hit? For example, the location it connects to spawn particles, or the angle of impact to trigger reaction animations? Or do you just need to know “there was a hit”?

For the latter, using simple colliders and OnBeginOverlap messages is the best way, bar none.

For the former, it’s a little trickier, but in my opinion the best approach is the one used by Super Smash Bros; you “coat” the surface of the attacking weapon with sockets such that if you were to attach sphere components to each one, those spheres would make a pretty good rough outline of the shape of the weapon. Then, every frame, you do a swept sphere trace to the current position of each socket from its position in the previous frame. Since you’re using spheres, this system remains accurate even if the weapon is rotating from frame to frame (using a single box or capsule collider doesn’t work since swept shape tests can’t rotate the shape during the sweep).

This requires some additional logic setup though; every frame, you need to remember if a hit was registered by one of the traces. Once a hit registers, you need to disregard all other hits until a frame occurs where NO hits register (without this step, a sword might swing two of its spheres through an enemy across two frames and yield a total of four registered hits for a single impact).

Frankly I think that the overlap test is far superior but UE4 doesn’t report any sort of hit result data on overlaps (no inpact location or normal) and if you need that data, frame-by-frame sweeps are really the only way to go, unfortunately.

I do need to get the impact location and all the Hit Result stuff, so using a box or a sphere isn’t the way to go for me.

So, for this frame-to-frame sweep, you store the position of each socket on current frame (except obviously the first frame compared as that one doesn’t have a “previous frame”) and in the next frame you make the spheres extend from previous frame position to the current?

So, like this? (Crappy paint drawing incoming)

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Then you check if something has been hit. If it has been hit you include it in a “Exclude actors” so you don’t hit the same actor twice in the same animation. Is that right?
However, I feel that this is kinda cheap as the weapon doesn’t really extend that far. Can’t you do like a hit test with physics? Like if I make my weapon a skeletal mesh, wouldn’t I be able to use the actual mesh as a collision component or something?