Help with keeping part upright

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#1

I am trying to rewrite a Unity code in LUA but I’m having trouble rewriting it. My current code doesn’t react the same as the Unity code.

Unity Code:

public void UpdateUprightForce()
{
	Quaternion characterCurrent = transform.rotation;
	Quaternion toGoal = UtilsMath.ShortestRotation(_uprightJointTargetRot, characterCurrent);
	
	Vector3 rotAxis;
	float rotDegrees;
	
	toGoal.ToAngleAxis(out rotDegrees, out rotAxis);
	rotAxis.Normalize();
	
	float rotRadians = rotDegrees * Mathf.Deg2Rad;
	
	_RB.AddTorque((rotAxis * (rotRadians * uprightJointSpringStrength)) - (_RB.angularVelocity * _uprightJointSpringDamper))
}

My Code:

local defaultRot = CFrame.Angles(0, 0, math.rad(90))
local uprightJointSpringStrength = 50
local uprightJointSpringDamper = 10

local function UpdateUprightForce()
	local characterCurrent = RootPart.CFrame
	local toGoal = defaultRot:ToObjectSpace(characterCurrent)
	
	local rotAxis, rotRadians = toGoal:ToAxisAngle()
	local rotDegrees = math.deg(rotRadians)
	rotAxis = Vector3.new(rotAxis.X, rotAxis.Y, rotAxis.Z).Unit

	local torque = (rotAxis * (rotRadians * uprightJointSpringStrength)) - (RootPart.AssemblyAngularVelocity * uprightJointSpringDamper)
	RootPart:ApplyAngularImpulse(torque)
end

I’m following this video tutorial: https://www.youtube.com/watch?v=qdskE8PJy6Q&t=146s&ab_channel=ToyfulGames

#2

in Roblox there’s something called an AlignOrientation, use that instead

If you don’t want to use it, try

local defaultRot = CFrame.Angles(0, 0, math.rad(90))
local uprightJointSpringStrength = 50
local uprightJointSpringDamper = 10

local function UpdateUprightForce()
    local characterCurrent = RootPart.CFrame
    local toGoal = defaultRot:inverse() * characterCurrent -- Equivalent to UtilsMath.ShortestRotation(_uprightJointTargetRot, characterCurrent)
    
    local rotAxis, rotRadians = toGoal:toAxisAngle()
    local rotDegrees = math.deg(rotRadians)
    rotAxis = Vector3.new(rotAxis.x, rotAxis.y, rotAxis.z).unit -- Adjusting for differences in vector notation

    local torque = rotAxis * (rotDegrees * uprightJointSpringStrength) - RootPart.AssemblyAngularVelocity * uprightJointSpringDamper
    RootPart:ApplyTorque(torque)
end
#3

Uhh. I tried adjusting the stiffness and the damping but it doesn’t really fix this issue:

#4

im so confused now, what exactly are you using

#5

I tried the script you provided.

#6

I honestly have no idea atp sorry

#7

Hm. This should be possible with two constraints, a SpringConstraint, and a PrismaticConstraint.

#8

But those will be laggy and not very good than code.

#9

This is very wrong. Constraints are very optimized, programming physics will definitely be more taxxing and less optimized, especially if you don’t know what you’re doing. Use the constraints.

#10

Oh. Maybe some other time but I want to fix this problem.

#11

Yes, using constraints will fix your problem. They’re the simplest thing.

#13

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