Question about CFrame:ToObjectSpace - why do I get a negative relative position?

[mooonc0w (Sauron)]

Hello
I have 2 parts one above another, no rotations:
GreenPart with position 10, 8, 5
OrangePart with position 10, 11, 5

I want to see what is the position of the OrangePart in relation to the GreenPart
When I call

local cf =  workspace.OrangePart.CFrame:ToObjectSpace(workspace.GreenPart.CFrame)
print(cf.Position)

I get 0, -3, 0
However I expect to get 0, 3, 0 , because I am translating the CFrame of the OrangePart in the coordinate system of the GreenPart and the OrangePart is 3 studs above it.

What do I miss here?

Thanks

[Scottifly]

I think it needs to be by worldspace because now it’s measuring the orange part’s relation to the green which is -3.
Of couse this is only if you want the distance measured according to the orientation of the world’s x, y, & z axes.

[ThanksRoBama (Emma)]

A:ToObjectSpace(B) does not convert A to Bs coordinate system, it does the opposite. It converts B to As coordinate system. Or in other words, it computes “B relative to A”. “GreenPart relative to OrangePart” is (0, -3, 0) (assuming OrangePart is not rotated), so you’re actually getting the expected output.

[mooonc0w (Sauron)]

This is from Roblox docs:

" To find the CFrame of the football relative to the blue player:
footballCF:ToObjectSpace(bluePlayerCF)"

In this example are we converting the ball’s position to player’s coordinate system or we are converting player’s position to ball’s coordinate system?

[vrs2210]

You’re getting the ball’s CFrame relative to the player’s CFrame, which is the same as seeing the ball in the player’s coordinates system.

[mooonc0w (Sauron)]

The player is positioned at 10,8,5
The ball is positioned at 10, 11, 5 (3 studs above the player)

What should be the position of the ball in players coordinate system?
0, 3, 0
or
0, -3, 0
?

[vrs2210]

It should be 3 studs above the player then, though Roblox may see it the opposite way.