Question about Motor6Ds

[matt1020304050]

So I have a model. A tank, with several parts that are welded to one base part.

I want to tween the Motor6D’s C0 position so I can basically use that to move the model from point a → b

But when I put the C0 position as the position of a part (Point B) it doesn’t even go close. What am I doing wrong here? How does one use a M6D’s position property properly?

https://gyazo.com/3d6a44d97126b39cf698f527e34be7da

[Dev_Peashie]

So, all parts of your tank are welded by Motor6d’s? and you want to change the motor6d position of C0 of a part in tank to “Point B position”. But what is Point B part? An external part that doesn belong to tank? and that Point B position is a World Coordinate position of that part?

That will never work, cause motor6d needs a relative position, relative to where is welded, it wont accept a world coordinate.

Example, if you change pos of C0 of a motor6d, to 5 studs, that would be 5 studs away from its original position.
If you have a part in workspace with a coordinate position of 500, and you use that 500 to update the motor6d, that would be 500 studs away from the origin point of the motor6d.

[matt1020304050]

Damn, so how do I go about this then?

I want to create a tank that can rotate it’s cannon on top. And also be able to move (the entire model and rotate) and be able to tween from position to position. How would I go about this?

[dthecoolest]

@matt1020304050

C0 position as the position of a part (Point B)

Yep as @Dev_Peashie mentioned with the object space example.

@dthecoolest

World CFrame relative to Motor6D/Weld space

Ok, now that we have understood what a weld can do, so now the question is how do we manipulate it via script without breaking the weld? The answer is to modify the offsets C0 and C1. Unfortunately this goes into CFrame:Inverse() territory which is a bit more complex and not accounted for in this tutorial however I will just point out the math properties during the derivation

--Starting from the weld equation

part1.CFrame * C1 == Part0.CFrame * C0

--Apply Part0.CFrame:Inverse() to the left hand side of both equations

Part0.CFrame:Inverse()*part1.CFrame * C1 = Part0.CFrame:Inverse()*Part0.CFrame * C0

--Apply CFrame:Inverse() * CFrame = CFrame.new(), CFrame Inverse property
Part0.CFrame:Inverse()*part1.CFrame * C1 = CFrame.new() * C0

--CFrame.new() *anyCFrame = anyCFrame, Identity CFrame property
Part0.CFrame:Inverse()*part1.CFrame * C1 =  C0
--Rearrange equation, swap sides
C0 = Part0.CFrame:Inverse()*part1.CFrame * C1

--We want part1 CFrame to equal some CFrame like CFrame.lookAt()

C0 = Part0.CFrame:Inverse()*CFrame.lookAt(part1, part2) * C1

Using this knowledge, we have derived one very useful CFrame formula. However you can use a formmula to make it work for Motor6Ds. I have used it in my Motor6D turret module.

Here is what it looks like in function form and an example when applies to a common Motor6D rig like R6:

local motor = script.Parent
local target = workspace.Target

local function worldCFrameRotationToC0ObjectSpace(motor6DJoint,worldCFrame)
	local part1CF = motor6DJoint.Part1.CFrame
	local part0 = motor6DJoint.Part0
	local c1Store = motor6DJoint.C1
	local c0Store = motor6DJoint.C0
	local relativeToPart0 = part0.CFrame:inverse() * worldCFrame * c1Store
	
	local goalC0CFrame = relativeToPart0
		
	return goalC0CFrame
end

while true do
	task.wait()
	motor.C0 = worldCFrameRotationToC0ObjectSpace(motor, target.CFrame)
end

//devforum-uploads.s3.dualstack.us-east-2.amazonaws.com/uploads/original/4X/8/f/7/8f79bc91e1b67d13538dd3c6b08a49931d3b2fb3.mp4

Wow it functions as if it’s just a regular part and you are simply setting the parts CFrame!

[matt1020304050]

Thank you, I read through just about all of your post. Maybe I missed it, but I didn’t see anything pertaining to how to move a part that contains welds or M6D.

How would I go about moving a part (base) like for example a car has a base and 4 wheels. If I move the base, I need to move the wheels with it. This part I can’t seem to figure out. If it’s in your tutorial though can you point out which part, I must of missed it if so. It’s hard to read that much text and keep focus on every aspect when it’s brand new information to me.

[Dev_Peashie]

What you mean?.. if the wheels are welded by WeldContraints or by Motor6d, the wheels will move along with the “base” primary part of the model

[matt1020304050]

I previously had that, and when I tried to change the Position of the part it instantly detatched all the welds and flung off.

wait(3)

local tweenService = game:GetService("TweenService")

local part1 = script.Parent

local part2 = game.Workspace.FacePart -- the destination part

local goal = Vector3.new(part2.Position)

local info = TweenInfo.new(1, Enum.EasingStyle.Linear) -- Tween for 1 second with linear easing

local tween = tweenService:Create(part1.Base, info, {Position = goal})

tween:Play()

https://gyazo.com/0a1eecb47acbe89a85522ee9e630dbb6

[Dev_Peashie]

Thats because you are tweening the Position and not the CFrame.
If you tween the CFrame property all welded parts by a WeldConstraint will move along with the model, if you tween the position those parts will not move

Should be like this:
local goal = part2.CFrame
local tween = tweenService:Create(part1.Base, info, {CFrame = goal})

[matt1020304050]

Oh that’s what I was doing wrong. Thank you both!