Rotate Weld.C0 on Specific Axis

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#1

I am looking to rotate the C0 of a weld on a specific axis. Not along the Global or Local axis but on an undetermined axis.

An example being if I wanted to rotate this part in the direction the black arrow is facing
So that it would rotate from this:
image
To this:
image

I am having trouble figuring out the CFrame math for this. Any help would be appreciated!

#2

This should work, derived it from formula in my CFrame tutorial.

The rotation should occur in any axis however it’s set to the center of part1 to a target point in this case, and the rotation is set at the center of the part1, let me know if you want to change the center of rotation.

It uses world space axis rotation howeverr with a specified axis using CFrame.fromAxisAngles:

--Evaera arrow adornment
--https://gist.github.com/evaera/735f23c67c2c173cfed2955f357b03a3
local function arrow(name, from, to, color, scale, alwaysOnTop : boolean)
	if alwaysOnTop == nil then
		alwaysOnTop = true
	end
	
	color = color or BrickColor.random().Color
	scale = scale or 1

	if typeof(from) == "Instance" then
		if from:IsA("BasePart") then

			from = from.CFrame
		elseif from:IsA("Attachment") then
			from = from.WorldCFrame
		end

		if to ~= nil then
			from = from.p
		end
	end

	if typeof(to) == "Instance" then
		if to:IsA("BasePart") then
			to = to.Position
		elseif to:IsA("Attachment") then
			to = to.WorldPosition
		end
	end

	if typeof(from) == "CFrame" and to == nil then
		local look = from.lookVector
		to = from.p
		from = to + (look * -10)
	end

	if to == nil then
		to = from
		from = to + Vector3.new(0, 10, 0)
	end

	assert(typeof(from) == "Vector3" and typeof(to) == "Vector3", "Passed parameters are of invalid types")

	local container = workspace:FindFirstChild("Arrows") or Instance.new("Folder")
	container.Name = "Arrows"
	container.Parent = workspace

	local shaft = container:FindFirstChild(name .. "_shaft") or Instance.new("CylinderHandleAdornment")

	shaft.Height = (from - to).magnitude - 2

	shaft.CFrame = CFrame.lookAt(
		((from + to)/2) - ((to - from).unit * 1),
		to
	)

	if shaft.Parent == nil then
		shaft.Name = name .. "_shaft"
		shaft.Color3 = color
		shaft.Radius = 0.15
		shaft.Adornee = workspace.Terrain
		shaft.Transparency = 0
		shaft.Radius = 0.15 * scale
		shaft.Transparency = 0
		shaft.AlwaysOnTop = alwaysOnTop
		shaft.ZIndex = 5 - math.ceil(scale)
	end

	shaft.Parent = container

	local pointy = container:FindFirstChild(name .. "_head") or Instance.new("ConeHandleAdornment")

	scale = scale == 1 and 1 or 1.4

	if pointy.Parent == nil then
		pointy.Name = name .. "_head"
		pointy.Color3 = color
		pointy.Radius = 0.5 * scale
		pointy.Transparency = 0
		pointy.Adornee = workspace.Terrain
		pointy.Height = 2 * scale
		pointy.AlwaysOnTop = alwaysOnTop
		pointy.ZIndex = 5 - math.ceil(scale)
	end

	pointy.CFrame = CFrame.lookAt((CFrame.lookAt(to, from) * CFrame.new(0, 0, -2 - ((scale-1)/2))).p, to)

	pointy.Parent = container

	if scale == 1 then
		arrow(name .. "_backdrop", from, to, Color3.new(0, 0, 0), 2, alwaysOnTop)
	end
	
	return shaft, pointy
end

local weld = script.Parent
local part1 = weld.Part1
local targetPoint = workspace.Target


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

	return relativeToPart0
end

local dt = 0.0001

targetPoint.Position = part1.Position+Vector3.new(0,5,0)

while true do
	local rotationAxis = (targetPoint.Position - part1.Position)
	arrow("Test", part1, targetPoint.Position, nil, nil, false)
	local rotationCFrame = CFrame.fromAxisAngle(rotationAxis.Unit,dt*2.5)
	
	local goalWorldSpaceCFrame = (rotationCFrame*part1.CFrame).Rotation + part1.CFrame.Position
	weld.C0 = worldCFrameRotationToC0ObjectSpace(weld, goalWorldSpaceCFrame)
	dt = task.wait()
end