Hello, so I’m trying to make a turret rotate to face the players mouse. I am using Hingeconstraint with Servo.
This is what it does right now

local Plr = game.Players.LocalPlayer
local PlrMouse = Plr:GetMouse()
PlrMouse.TargetFilter = script.Value.Value.Parent.Parent
local UIS = game:GetService('UserInputService')
local function turretFunction()
local RadAngle = math.acos(math.clamp(script.Value.Value.CFrame.LookVector.Unit:Dot(PlrMouse.UnitRay.Direction), -1, 1))
local VectorDot = script.Value.Value.CFrame.LookVector.Unit:Dot(PlrMouse.UnitRay.Direction)
local DegAngle = math.deg(RadAngle)
if VectorDot < 0 then
script.Value.Value.HingeConstraint.TargetAngle = script.Value.Value.HingeConstraint.CurrentAngle - DegAngle
elseif VectorDot > 0 then
script.Value.Value.HingeConstraint.TargetAngle = script.Value.Value.HingeConstraint.CurrentAngle + DegAngle
end
end
PlrMouse.Move:Connect(turretFunction)

You should assign DegAngle directly to TargetAngle, not sum this value with the CurrentAngle.

That will fix the problem in the video, but you’ve got a problem with the math resolving the angle. The two vector’s used with Dot Product to find the cosine of the angle need to have the same origin. script.Value.Value.CFrame.LookVector is in world space so it’s origin is 0,0,0. According to the api;PlrMouse.UnitRay.Direction is not in world space, so it’s origin is CurrentCamera’s position.

You’ll want to use a vector from script.Value.Value.CFrame.Position to PlrMouse.Hit.Position instead of the UnitRay.

local vecA = script.Value.Value.CFrame.LookVector.Unit
local vecB = (PlrMouse.Hit.Position - script.Value.Value.CFrame.Position).Unit
local theta = math.acos(vecA:Dot(vecB))

This page has more information on using Dot Product with the inverse cosine to resolve theta.

Are you sure I don’t have to add/subtract with the CurrentAngle. Because the same problem is still happening with your code. My thought process is that since it is getting the angle between the two vectors it is not taking that into respect with how big of an angle it currently is. Also just realised that maybe I have to reset the target angle to 0 after?

Oh you’re right, issue is the vectors are backwards. My code should still fix the not of same origin issue. I think you should swap the vectors around so the mouse vector makes vector A, and the barrel makes vector B.

That way the resulting theta value is how far it needs to move to make vector B align with vector A.

You would need to project the vecB across the vecA space so it’s in 2d to get the exact angle of rotation around just the Y axis. Using inverse tangent like @nicemike40’s suggestion would remedy that issue. (Remember to find the mouse hit position vector that has the hingeconstraint as it’s origin)

Yea so I used your code, and it works but only if I subtract 90 on the final angle, since for some it always faces 90 degrees away from the mouse position. Subtracting 90 fixes it, but is there another way to fix it?