Creating placement system with surface normals

[C_ozmo (Lucas)]

I’m not really sure how to describe my problem so I have created a diagram to explain it. I want to be able to place parts on walls and rotated parts flush with the sides. I presume you would use raycasts and surface normals for this but I am not quite sure.

[Katrist]

Maybe this can help?

How to Use Normal Vector to Align Part to Ramp

The responses in this thread are incorrect. The surface normal is essentially a vector that points directly away from the surface. One easy way of using this data is CFrame.new(part_pos, part_pos + normal). This will cause the object to ‘look at’ the surface normal, thus “aligned” with it. You can simply rotate this CFrame to orient it in whichever way you want relative to the surface. Refer to thread: Explanation of Surface Normal?

To get the normal you can just do RaycastResult.Normal.

[C_ozmo (Lucas)]

Thanks for pointing me in the right direction. This has worked for me for the most part. Do you have any idea how I would make these blocks face the other way upon being placed (as shown)

[Katrist]

You can just rotate the CFrame relative to the normal which only needs a little bit of experimenting to get right.

Eg:

part.CFrame *= CFrame.Angles(0, math.rad(90), 0)