Rotate a CFrame orientation like a vector

[01_0101100 (SuperUser)]

Yeah but it doesn’t work. I’m gonna try again and yes you are right it should work as I am using it to fix the same problem earlier in the code.

[dthecoolest]

The vocab being used here is confusing.

From my understanding isn’t this all about doing rotations in world space or object space?

If so then order of operations matters a lot and I would recommend trying all permutations of CFrame and it could be the difference between the perfect working formula vs non working one, as seen in my tutorial below for there examples.

Also the C0 formula seems off it should the the Part0 being inversed first then multiplied by your desired rotation CFrame like in my CFrame tutorial derived from the weld CFrame equation from the understanding CFrames article:

Neck.C0 = CFrame.new(Neck.C0.Position)  * NeckConnect.CFrame.Rotation:Inverse() *CurrentRotation

@dthecoolest

weld.C1 = attachment1.CFrame

weld.Part1 = attachment1.Parent

weld.Parent = attachment1.Parent --any parent under workspace to make the weld active

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.

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

[01_0101100 (SuperUser)]

I didn’t test your solution but in mine the only thing that didn’t work was the fact that some axises where swapped when the torso rotation was not 0. Maybe you are right but I don’t think so. By the looks of it, the glitched behaviour is very similar from when applying a 90 degrees offset to the phone rotation so the camera would face the right way. I fixed it using ToWorldSpace() but it doesn’t work here. We will have to see if your thing works.