Why is it CFrame * CFrame instead of CFrame + CFrame?

[Hokker3]

Sometimes in code, I see stuff like

model:SetPrimaryPartCFrame(game.Workspace.Part.CFrame * offsetCFrame)

My question is, shouldn’t it be + before the offsetCFrame instead of *? Since you basically take the part’s CFrame and add an offset to it. Is there something special about CFrames regarding this? Please explain

[AstralBlu_e (Astral)]

Well I dont know how to help here but I think these posts can help you:

How to think about Vectors

ROBLOX uses vectors to represent positions and directions of things in the game world. This is a more mathy post than the CFrame one, but there are no proofs. This is all very useful information. ROBLOX has a Vector3 and Vector2 class which handles most vector operations. For the purpose of this post, I’ll be describing most things in terms of 2D vectors. All standards are ROBLOX standards (such as x being right, y being up…) Vector Basics A vector is a number that can contain any amount of…

How to think about CFrames

#CFrames are how ROBLOX represents the 3D position and orientation of objects in the game world. Understanding how these work can lead to easier to write, easier to read, and overall more efficient CFrame code. If you’ve ever done something like: print(CFrame.new()) you know that it gives you 12 numbers. What do these numbers mean? Well before we start, let’s think about CFrame.lookVector. lookVector is a unit vector (vector with a magnitude of 1) that points in the direction the CFrame is f…

[meguy1]

The reason for this is that it simply doesn’t make sense to add two CFrames together (it will give you an error).

CFrames contain both positional and rotational information. Even though it makes sense to add a position to a position, it doesn’t make sense to add a 3D rotation to another 3D rotation. Hence, you cannot add two CFrames.

You could add a Vector3 to a CFrame, because a Vector3 contains only positional information:

print(myCFrame + myVector3)

This basically takes the CFrame (position and rotation) and translates it by the given Vector3 (position only).

Also keep in mind that CFrames are stored as matrices, and when we use the * operator on matrices, we are actually performing matrix multiplication, which is necessary to “add” two 3D rotations.

Alternatively, if you are only interested in the positional component of the offsetCFrame, you could use:

print(workspace.Part.CFrame + offsetCFrame.Position)