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Comment by praptak | Hacker News Reader

I have played a bullet hell type game (2d) where bullets were actual 2d objects (mostly discs) but the player ship's hitbox was just a point, even though the ship itself was drawn as a somewhat bigger shape.

I guess this made the collision detection a bit faster and also made the game more dramatic - the close calls were bullets passing through the ship.

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FFXIV has the same point mass hitbox as there's a large discrepancy for player model size.

This caused problems for one of our tanks about two expansions ago where his class' combat stance combined with being the largest race had his character model stand entirely outside the hitbox.

FFXIV, like (some?) other MMOs, also has no collisions between player characters. So you are frequently expected to “stack” your hit“boxes” at the same point.

It would be interesting to see if that was a game design decision to allow for the game to be more dramatic.

There's something called "Coyote Time" which is named after Wile E. Coyote and him staying in the air for a few seconds before gravity takes effect. Often in platformers, there's an invisible collision box added after cliffs so that if the user was slightly late pressing jump at the edge of the cliff, they would still make it as the invisible collision box would provide an extra step. It's an example of improving gameplay and game feel without being realistic.

> It would be interesting to see if that was a game design decision to allow for the game to be more dramatic.

It is, it's called "grazing."

Ah interesting, not come across that term for game design, thanks!

It's a term used by players more so than designers I think - you usually get more points or something for getting as close as possible to bullets without getting hit, and some really dense patterns will require it, because the bullet sprites will practically be filling the screen.

It's possibly also worth mentioning for people unfamiliar with danmaku games that most are one hit kills against the player.

Small hitboxes are just small hitboxes. "Grazing" specifically means closely approaching things that are harmful to touch, usually because the game rewards it in some way. This makes the game more fun by encouraging the player to take risks. It's been around for a long time, but AFAIK the first game to use it as a core mechanic was Psyvariar (2000), where it's used to power up your ship.

Seems like it should be older than this. Lotus Land Story (Touhou Project #4) has a graze counter, but being a doujin game it should be riffing off of other games that use graze for scoring or as a mechanic.

If it's called Coyote Time, then the box needs to disappear after the grace period, right? I mean if someone stops over the invisible box and never presses the button they should fall after all.

There's a few ways of implementing these input grace periods. For example just allowing jumps to trigger within a time period after last contact with the ground. No extra collision needed. It doesn't need to be taken too literally.

Having your ship's hitbox be a single pixel is pretty standard in bullet-hell games. I'd say "drama" probably figured into that choice, it's really common to see enemies shoot out a little arc of bullets that slowly spread out as they travel, and watching a decent player fly their ship right through the gaps in that arc is cool.

Of course, that's one of those things you can't tell the players. Like that game where the first killing blow (within some timeout) on the player automatically misses. It makes it more fun.

Nah, it's actually an explicit conceit in danmaku games (the style described by GP). In Touhou, when you press shift to move slowly, it shows your hitbox as that single point. There's no point in hiding it from the player, because there is no way to even survive if the hitbox weren't a single point. There are often only a few pixels of clearance in between the waves of bullets.

Consider this: https://www.youtube.com/watch?v=AY7QEEnSGVU

EDIT: Or this, https://www.youtube.com/watch?v=JJgy5skcMJI

At the end, you can really see the boss's frustration with the player as the beautifully ordered patterns devolve into an angry display of brute force as she throws every kind of bullet in the game at you at once.

I think it was explicit in the instructions.

Point to disc collision doesn't seem like it would be significantly simpler than disc to disc collision. In both cases the most expensive computation is calculating the square distance between the objects, which can be done with a table lookup and an addition. In point to disc collision you then determine if the squared distance is less than the squared radius of the disc, in which case you have a collision. The only difference in disc-to-disc collision is that you compare to the square sum of both radii instead.

Moreover, this kind of collision system is often used in games on systems where the hardware is capable of reporting pixel perfect sprite overlaps anyway, so I think you're on track when you say it's for dramatic effect. IME it's also frustrating in games where this isn't the case because you feel cheated when you die because a shot barely grazed some antenna.

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