Trying to apply CFrame rotation in only one axis on a welded basepart

OneRubySky · April 11, 2020, 3:44am

The following code prints:
0, -15, 90 | 0, 0, 0
0, 0, 0 | 0, 0, 0

but the turret is not rotating at all.

while true do
	if target.Value ~= nil then
		local v = CFrame.new(turret.Position, target.Value.Position):VectorToObjectSpace()
		print(turret.Orientation, v)
		turret.Orientation = v
		print(turret.Orientation, v)
	end
	wait(1/20)
end

What am I doing wrong?

sjr04 · April 11, 2020, 3:46am

It takes a Vector3 argument.

OneRubySky · April 11, 2020, 3:48am

Sorry, i’m complexly lost in CFrames. They use a different rotational system than the ‘Rotation’ option on Baseparts? How do I pick out one axis from the rotation of a CFrame and apply it to a Basepart?

**from a CFrame made from two points

BrioX · April 11, 2020, 4:00am

If you’re wanting to change the orientation of the turret, it would be best to alter its CFrame, not orientation

AstroCode · April 11, 2020, 9:19am

I’m not a CFrame expert, so this comes from my own tinkering.

If you want to rotate about a CFrame’s up/look/right vectors, you can use CFrame.Angles:

local CF = CFrame.new() -- the starting CFrame

RunService.Heartbeat:Connect(function()
    Part.CFrame = CF * CFrame.Angles(0, math.pi * tick() % (2 * math.pi), 0)
end)

That would look like this

If you want to rotate about an arbitrary axis, you can use CFrame.fromAxisAngle:

local CF = CFrame.new() -- the starting CFrame
local Axis = Vector3.new() -- the axis to rotate about

RunService.Heartbeat:Connect(function()
	Part.CFrame =
		CFrame.fromAxisAngle(
			Axis,
			math.pi * tick() % (2 * math.pi)
		):Inverse()
		* (CF - CF.Position)
		+ CF.Position
end)

I wish I could tell you why this works, but like I said, I figured this out through experimentation. There is probably a better solution.

OneRubySky · April 11, 2020, 3:43pm

Well I have tried multiplying by CFrame.angles before. Might it have anything to do with the part being welded to a larger model?

AstroCode · April 11, 2020, 4:09pm

If it’s welded then you should be modifying the C0/C1 properties and not the CFrame directly.

OneRubySky · April 11, 2020, 7:05pm

Here, this is what I’m trying to do but now i’m having trouble converting values, and it’s still being glitchy as well.

while true do
	if target.Value ~= nil then
		local n = CFrame.new(turret.Position, target.Value.Position):()
		local weld = turret:FindFirstChildWhichIsA('Weld')
		weld.C1 = weld.C1 * CFrame.fromAxisAngle(0, n.Y, 0)
		break
	end
	wait(1/20)
end

The break is for debugging.

OneRubySky · April 11, 2020, 9:24pm

How do I modify them if they are Userdatas?

AstroCode · April 12, 2020, 6:17am

I’m not sure what you’re trying to do here. On the third line, you have a :() that doesn’t do anything. On the fifth line, I don’t think you’re using fromAxisAngle correctly. Also, what do you mean that it’s being glitchy?

Anyway, this post piqued my interest so I had a go at it myself.

Turret.rbxl (31.5 KB)