Ask a Game Dev
Here’s the thing – animations don’t inherently have any sort of [collision detection]. They’re a lot like shadow puppets – they have no mass, they have no physics, they just exist as projections onto a screen. Animations just exist in space – they’ll pass through anything that occupies that same space because there’s no actual matter that can collide.Since shadow puppets have no mass, they can’t physically interact with anything. We can pretend to have them interact by acting as if they were affected by something – a punch, a throw, a kiss, a hug, etc. This is what animators do – they sculpt motion over time and try to line things up if they can. “Canned” interactions are basically paired or group animations that are designed to play simultaneously in order to make the overall motion believable. A shoulder throw won’t be believable if the victim being thrown doesn’t move in tandem with the attacker doing the throwing. We also often have generic reactions (e.g. getting punched in the face, getting shot, getting knocked down, etc.) but those don’t look as good as tailored animations meant to go together.Paired interactions are more expensive to build than generic animations – you need to build the animation for the skeletons of the performers, which means that it won’t work for a different skeleton, and those paired animations can only be used together under specific circumstances (e.g. a shoulder throw shouldn’t be done if there isn’t enough space for the victim to land on the ground). This is one reason why Call of Duty’s executions work – everybody uses the same skeleton, so the same animations can be played on every character. This won’t work in a game where different characters have different skeletons – the normal shoulder throw animations won’t work if one character is a pixie and the other is a dragon.Beyond this, there’s also the issue of clothing and character model. The animations might not clip, but enormous chunks of material on the character models (like flashy armor) will clip through if the animations don’t account for those things. This is one reason why you often see clipping issues during in-game cinematics where the player’s flashy wardrobe causes clipping issues because the animators never expected the player’s shoulder pads to be as enormous as they are.[Join us on Discord] and/or [Support us on Patreon]Got a burning question you want answered?