R15 Humanoids Gain Large Amounts of Velocity When Their HumanoidRootPart Touches the Ground

[Dekkonot]

When a Humanoid in R15’s HumanoidRootPart touches the ground, it freaks out massively and slide off into the distance. No, seriously:

It slides like that until it falls off the BasePlate. Presumably it would be forever if it didn’t fall.

The model that contains these four lovely humanoids is located here:
humanoid-touching-ground-glitch.rbxm (4.2 KB)

To repo this, you can either set the HipHeight of an R15 model to 0 as I did above or you can cause a bug to occur that makes the HipHeight property not be respected. Either one will cause it to happen, which is why I explicitly say it’s a problem with it touching the ground and not a problem with a HipHeight of 0.

The expected behavior here is that it performs like the R6 example, where it just sits there sadly on the ground instead of zooming off.

[ContextLost]

For better or worse this is intentional behavior. This “my butt is caught on a corner” panic mode.

Humanoid floor sensor is currently based on a cluster of raycasts. Of course it’s possible for part the character to get caught on a corner and none of the raycasts hit it. So to avoid a player getting stuck like this, if the bottom of any of the Humanoid’s parts contacts anything, it will try to slide away from it.