[Game-breaking] Corescript ragdoll system sets avatar limb positions to Vector3(nan,nan,nan) if triggered while an animation is playing

Noble_Draconian · October 24, 2022, 8:33pm

Reproduction Steps

Currently, as of 10/24/22, if a player gets ragdolled by Roblox’s built-in ragdoll system (can be found in the corescripts) while an animation with Action priority is running in a loop, various limbs of the player’s avatar are positioned to Vector3(nan,nan,nan). This causes all sorts of wild behaviors with the avatar & the humanoid, consistently breaking game logic.

Steps to reproduce:

Open the attached reproduction file
Enable the “China” test player profile under Test → Player:
Run a playsolo session
Observe the “action” priority animation being ran on the avatar
Reset the avatar (via the escape menu)
Observe that the avatar has had various limbs set to Vector3(nan,nan,nan) and is rapidly blinking, among other odd behaviors.

NaNRagdollIssue.rbxl (36.7 KB)

My production game, Super Skyward Towers has recently started getting odd behaviors around the same time this reported bug started occurring. If players are ragdolled, the run animation now continues playing even if they aren’t walking. This was not happening before. It’s possible some engine change is the root cause of this bug.

EDIT : This is critical. This is literally breaking our production game. If a player is in a fall-scream state in our game and they get ragdolled, the nan position bug occurs. This was not happening before. It’s definitely related to an engine change.

Expected Behavior
It is expected that the corescript ragdoll system would ragdoll the player, regardless of what animations are running.

Actual Behavior
The corescript ragdoll system positions various avatar limbs to Vector3(nan,nan,nan) when triggered if there are “action” priority animations being ran on the avatar. It’s worth noting, both animations & the ragdoll system from the corescripts both modify the joints / motor6Ds internally, so there might be some correlation there.

Workaround
None

Issue Area: Engine
Issue Type: Other
Impact: High
Frequency: Constantly
Date First Experienced: 2022-10-24 00:10:00 (-04:00)

Noble_Draconian · October 24, 2022, 9:29pm

Urgent bump, this is breaking our game in production. A recent engine change is causing this issue.

weakroblox35 · October 24, 2022, 11:18pm

Can replicate, in our game if a player dies they get “flinched”, just a little fling that lasts for 0.18 seconds, (bodyvelocity) however if the player DIES while an animation is playing, they get fling in the void. (This is due to the animation still playing and ragdolls interfering.)

Noble_Draconian · October 25, 2022, 9:11pm

This is still happening as of 10/25/22.

ContextLost · October 26, 2022, 4:40pm

Since I assume you took your own copy of the scripts, can you try commenting out the call to ApplyJointVelocities.

I suspect that function may have been broken during an internal animation runtime rewrite.

Noble_Draconian · October 26, 2022, 11:11pm

I’ll give this a try! Will post results here.

Noble_Draconian · October 26, 2022, 11:39pm

Hey @ContextLost! Commenting out ApplyJointVelocities fixed the issue! I’ll leave it commented out as a temporary patch. Hopefully you folks fix the underlying engine issue

Quenty · October 28, 2022, 4:57am

FYI, ApplyJointVelocities has been broken for a while now. I had to fake it.

github.com/Quenty/NevermoreEngine

src/ragdoll/src/Shared/Rigging/RagdollMotorUtils.lua

667cf7630


      
          	local ok = pcall(function()
          		currentNetworkOwner = part:GetNetworkOwner()
          	end)
          	if ok then
          		return currentNetworkOwner == expectedNetworkOwner
          	end
          
          	return CharacterUtils.getPlayerFromCharacter(part) == expectedNetworkOwner
          end
          
          function RagdollMotorUtils.promiseVelocityRecordings(character, rigType)
          	assert(typeof(character) == "Instance" and character:IsA("Model"), "Bad character")
          	assert(EnumUtils.isOfType(Enum.HumanoidRigType, rigType), "Bad rigType")
          
          	local parts = {}
          
          	local rootPart = character:FindFirstChild("HumanoidRootPart")
          	if not rootPart then
          		return Promise.rejected("No humanoid root part")
          	end

m0bsterlobster · June 25, 2025, 9:58pm

Hey Noble!

Hope you’re doing well

Just wanted to let you know we’ll be closing this bug since Avatar Joint Upgrade should provide a native, robust ragdoll system, making this bug obsolete.

Please let us know if this issue is still blocking you and AJU won’t fix it, and we’ll reconsider whether or not we will invest engineering resources / its proper priority.

Best,
M0bsterLobster

Noble_Draconian · June 25, 2025, 9:59pm

Hi! I can take a look into this in about 40 minutes. Let me get back to you

Noble_Draconian · June 25, 2025, 11:26pm

@m0bsterlobster Heya!

I did some testing, it seems ApplyJointVelocities() does not NaN parts anymore from what I’ve tested.

With the new joint upgrade, If I have an animation playing and I trigger the ragdoll, will that preserve the position of the joints from the animation? With Roblox’s corescript ragdoll, if you don’t call ApplyJointVelocities(), the ragdoll will get put into a “t-pose” when triggered instead of preserving limb placement from the currently running animation.

If the answer to that is “yes”, then I believe this bug can be closed out as we’ll switch to the new joint system when time allows

Homeomorph · June 30, 2025, 7:26pm

Yes, you can see this in the Avatar Joint Upgrade demo place when your ragdoll.

system · July 14, 2025, 7:26pm

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