How to do hit detection for a fast and large projectile

[hello42]

Roblox currently has pretty bad .Touched detection for really fast moving projectiles, although they’re working on it as we speak. There are a couple good libraries you can use to remedy this temporarily, though:

Raycast Hitbox 4.01: For all your melee needs!

Current Version: V.4.01 Stable (09/21/2021) Upgrading from 3.xx to 4.0 Please note that V4 is not backwards compatible with V3. There are a few API changes that were introduced in V4 to better suit modern code etiquette. Here are the changes you need to know if you want to make your code compliant with V4: Raycast Hitbox 4.01: For all your melee needs! - #597 by TeamSwordphin Notable Features Accurate, performant, and easy to use! Use attachments or vectors to make your hitboxes in secon…

While it’s advertised as being used for melee, the hitbox method is really good if you’re looking to get something returned if it hits it while your projectile is moving at 1200 studs per second. Very performant as well.

Secondly, if you don’t want to use the Raycast Hitbox library, you could also use RotatedRegion3s, as they’re pretty simple to set up:

Rotated Region 3 Module

Update: This module has served its purpose, but with the release of the new spatial query API this post is obsolete. It will be left untouched for learning purposes, but it’s strongly recommended to check out the built-in api solution instead. Recently I took another crack at an old module I wrote some time back. The goal of this module is to provide users with a way to create Rotatable Region 3’s which is useful for too many reasons to list. Even though this module (older versions) has been …

I’m not extremely familiar with all of the functions of RotatedRegion3, but my only caution for you if you decide to use this is performance.

As always, you want to limit yourself on doing anything intense unless you absolutely have to - especially if you’re doing hit detection from the server. And creating a large Region3 (or subsets of Region3s to account for rotation?) with multiple FindPartsInRegion3 calls as well as accounting for potential numbers of parts (math.huge is a no-no) in a Region could be dangerous. Especially when it comes to creating it on every Heartbeat of the game.

Both methods account for your ‘player-grazing the part’ scenario. A 5, 5, 5 BasePart shouldn’t be that bad. Good luck on getting things to work on your end!