Problem with surface normals

[Herobrinekid1 (カイネ)]

Heya!!!

Currently im developing a game where each player gets the task to build a limb for a giant monster.

In the game the player gets a lot of freedom to customize their limb however they want. Theres just 1 problem… The method i use to retrieve the “Surface normal” of a part to position surface guis on doesnt work that well on cylinders/spheres.

Yes i could technically use the “Mouse.TargetSurface” to solve this issue but that also has a problem. Theres objects in the workspace that needs to be ignored. I cant just set “Mouse.TargetFilter” right now because that would break most of the game.

As you can see from these videos. The method i currently use works perfectly on cubes but on others well… not that well.

When hovering over a cube it prints out the normals numbers as ints.

But on others such as a sphere/cylinder it prints them as floats

Cube:

Cylinder/Sphere

Any help would be realy appreciated!! because as you can guess. Customization is the key component in the game so if i cant get this fixed then the game is basically dead.

Code i currently use to retreieve the surface normal of a part.

function Funcs:GetMouseTarget()
	local Params = RaycastParams.new()
	local Building = workspace.Assets.Building
	local Mouse = game.Players.LocalPlayer:GetMouse()
	local UnitRay = Mouse.UnitRay
	local Faces = {
		[Vector3.new(0,1,0)] = Enum.NormalId.Top,
		[Vector3.new(0,-1,0)] = Enum.NormalId.Bottom,
		[Vector3.new(0,0,-1)] = Enum.NormalId.Front,
		[Vector3.new(0,0,1)] = Enum.NormalId.Back,
		[Vector3.new(-1,0,0)] = Enum.NormalId.Left,
		[Vector3.new(1,0,0)] = Enum.NormalId.Right,
	}
	
	Params.FilterDescendantsInstances = {game.Players.LocalPlayer.Character,Building.Radius,Building.Objects.PrimaryPart,Building.Parent.Debris}
	Params.FilterType = Enum.RaycastFilterType.Exclude
	
	local A = workspace:Raycast(UnitRay.Origin,UnitRay.Direction*1000,Params)
	local Face = Faces[A.Normal] or Enum.NormalId.Front -- Returns "Front" as default to make sure it doesnt return nil.
	
	
	return A.Instance,A.Position,Face
end

[Ax1sAng1e (Pastor James)]

Try setting all the parts to 0,0,0 for orientation?
You might have to “rotate” the vector based on the object’s orientation.

[7z99 (cody)]

This happens because raycasting respects the geometry of the part the ray is cast onto. If you need a specific NormalId there are a couple options:

1- use mouse.TargetSurface, but be aware that the mouse doesn’t always guarantee support for devices like phones.
2- use the dot product on your “goal” normal and the vector that corresponds to a NormalId, whichever dot product is the largest would be the surface your cursor is closest to.

local userInputService = game:GetService('UserInputService')

local normalIds = Enum.NormalId:GetEnumItems()

local normalVectors = {}

for _, normalId in normalIds do
	normalVectors[normalId] = Vector3.FromNormalId(normalId)
end

local function getClosestNormalId(vector: Vector3)
	local closestDot, closestNormalId = -math.huge, nil
	
	for _, normalId in normalIds do
		local otherVector = normalVectors[normalId]
		
		local dot = vector:Dot(otherVector) -- how close vector is to otherVector
		
		if closestDot < dot then
			closestDot, closestNormalId = dot, normalId
		end
	end
	
	return closestNormalId
end

while true do
	local mouseLocation = userInputService:GetMouseLocation()
	
	local ray = workspace.CurrentCamera:ViewportPointToRay(mouseLocation.X, mouseLocation.Y)
	
	local raycast = workspace:Raycast(ray.Origin, ray.Direction * 1000)
	
	if raycast then
		local resultCFrame = (raycast.Instance :: BasePart).CFrame
		
		local normalRelative = resultCFrame:VectorToObjectSpace(raycast.Normal).Unit -- this will be the normal relative to the object, so it should have the length of approx. 1 taking into account floating point imprecision. 
		-- ^you should be able to remove the index for the unit vector, however if you want it for contingency it shouldn't be a hindrance for performance
		
		local closestNormalId = getClosestNormalId(normalRelative)
		
		script.Parent.TextLabel.Text = `Mouse is over {closestNormalId.Name} surface.`
	end
	
	task.wait()
end

[Herobrinekid1 (カイネ)]

You my man… Is a lifesaver!!! world/object space and math is like my achilles heel.