How to know if part is touching terrain

[jjadtru (Jad)]

How can i know if a part is touching the grass material of my terrain

[FroDev1002 (FroDev)]

May I ask in which case you plan to use this? For instance with a projectile the best methods of this could change, etc.

[jjadtru (Jad)]

I am using brush tool to place down cactus and some of them are place on the wrong terrain and I just want to make a console code to remove the ones on the grass terrain

[FroDev1002 (FroDev)]

Well in that case, lets wait for someone whos knows what they are doing to come to this post

[jjadtru (Jad)]

I made this but ists super inaccurate

local workspace = game:GetService("Workspace")

local function isTouchingGrass(part)
	local regionSize = Vector3.new(4, 4, 4) -- Small region around each part
	local partPosition = part.Position
	local region = Region3.new(partPosition - regionSize/2, partPosition + regionSize/2):ExpandToGrid(4)

	local material, _ = workspace.Terrain:ReadVoxels(region, 4)
	local size = material.Size

	for x = 1, size.X do
		for y = 1, size.Y do
			for z = 1, size.Z do
				print( material[x][y][z])
				if material[x][y][z] == Enum.Material.Grass then
					return true
				end
			end
		end
	end

	return false
end

for _, instance in pairs(workspace:GetDescendants()) do
	if instance:IsA("Part") and isTouchingGrass(instance) then
		
		script.Highlight:Clone().Parent = instance
	end
end

[tinctoriall (tinctorial)]

Usually, raycasting is your best bet.
Also always make sure to search up your posts’ topic, because chances are it’s already been answered.

Part Touching Terrain

If .Touched doesn’t work, then multiple Raycasting with a Whitelist containing only the Terrain should work. Since you’d only need to cast a handful of rays in a few directions from the center of your helicopter AND your rays only need to be ever so slightly longer than the helicopter’s distance from its center, those short rays won’t be resource-consuming, so that’s probably the most performant way to go.

You can do something like this:

local params = RaycastParams.new()
params.FilterDescendantsInstances = {workspace.Terrain}
params.FilterType = Enum.RaycastFilterType.Include

local ray = workspace:Raycast(script.Parent.Position, Vector3.new(0,-10,0) * 10, params) -- assuming script.Parent is a part
print(ray.Material) -- Enum.Material.Grass

Should work.

Hope this helps!

[tinctoriall (tinctorial)]

Also sorry to bump, but you should probably consider the limitations of the Highlight Instance (which is apparently limited to 31 Instances, enabled or not).
Maybe your code works flawlessly but that’s creating a bottleneck!

Highlight | Documentation - Roblox Creator Hub

[jjadtru (Jad)]

Thank you, i was just using it to visualize