How would i place Part A on a face of Part B with CFrame math

[B_lial]

what i want to accomplish ^^^

[dthecoolest]

Rigid Constraints/Welds, both can use attachments to help align the positions and orientation

Rigid constraint method:

Weld method:

local weld = Instance.new("Weld")

weld.C0 = attachment0.CFrame

weld.Part0 = attachment0.Parent

weld.C1 = attachment1.CFrame

weld.Part1 = attachment1.Parent

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

Manual method:

Part1.CFrame = Part0.CFrame*Part0.Attachment.CFrame*Part1.Attachment.CFrame:Inverse()

[B_lial]

This is not exactly what i was hoping for, I can provide a better example if you want of what i will use this for

[B_lial]

https://i.gyazo.com/5815a9ce2a65c827c348393c1da7e78c.mp4

[dthecoolest]

Oh alright, next time please put your use case in your post as well. This problem is alignment, where you want a part to align to a surface.

@dthecoolest

CFrame aligning vectors

Usually, we want to align a CFrame such that it’s UpVector matches another arbitrary vector for example if we want to align a part to a surface normal vector.

One common method that is seen is the CFrame.lookAt method

CFrame.lookAt(pos1, pos1 + newDirection)

Unfortunately, the above CFrame method forcefully also generates the rest of the vectors and doesn’t allow for much control unless you mess around with the third parameter the “UpVector”

Or you could use @EgoMooses advanced CFrame technique like in this post .

[B_lial]

I have tried using lookAt in the past and it does really weird stuff, dont know if i just dont know how to properly use it. ive looked at many things about it and it is still typically very buggy

this is what it returns in attempts to print the set lookAt Cframe