Explosion not detecting part

Testing Explosion.rbxl (16.8 KB)

The following place demonstrates my issue. When I plant any explosion object in, and it hits a part in the Model, it should print where in the model that part is, however those specific parts are not being detected.

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This is very interesting. I wasn’t able to find a solution, but it seems that when I scale the ring in the repro down, explosion hits start being detected. For some reason, these explosions really hate big parts?

Explosion hit detection is based on magnitude. So large parts are not detected since position of the part is far off.

The work around is to create a new unanchored cancollide true sphere and use :GetTouchingParts() which works on ungrounded parts. Then immediately destroy. The Roblox RPG does this.

I’d you need anchored parts, or can collide parts it may be more difficult. Personally I use a raycasting method that raycasts in a randomly evenly distributed manner so I can calculate percent damage and/or exposure. This seems decently performant.


I am actually intrigued by the Sphere concept.

So if logic assumes to be right (Never assume kids)

local part = Instance.new("Part", workspace)
	part.Shape = Enum.PartType.Ball
	part.Size = Vector3.new(2,2,2) * obj.BlastRadius
	part.CFrame = CFrame.new(obj.Position)
	part.Anchored = true
	part.CanCollide = true
	part.Transparency = 1
	for i,v in pairs(part:GetTouchingParts()) do
		--Do Hit Logic
	delay(0.1, function()

Should work in practice?

Some notes:

  • There’s no need to delay destruction! You can destroy immediately.
  • Don’t parent until you’ve set all properties. This is a significant performance cost.
  • The part must be unanchored
  • This only detects parts that are unanchored and CanCollide true.
  • Disclaimer: this is still technically a hack. It may stop working.


local part = Instance.new("Part")
part.Anchored = false
part.CanCollide = true
part.CFrame = CFrame.new(explosion.Position)
part.Shape = Enum.PartType.Ball
part.Size = Vector3.new(2, 2, 2) * explosion.BlastRadius)
part.Parent = workspace -- Maybe parent to camera on server so it doesn't even try to replicate. I don't _think_ this is an issue. I'm not sure. 

local parts = part:GetTouchingParts()

for _, part in pairs(part:GetTouchingParts()) do
    -- do Logic

Explanation should you want one:

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