Terrain Triangle

local X, Z = 15, 15

local wedge = Instance.new("WedgePart");
wedge.Anchored = true;
wedge.TopSurface = Enum.SurfaceType.Smooth;
wedge.BottomSurface = Enum.SurfaceType.Smooth;

local function draw3dTriangle(a, b, c)
    local ab, ac, bc = b - a, c - a, c - b;
    local abd, acd, bcd = ab:Dot(ab), ac:Dot(ac), bc:Dot(bc);

    if (abd > acd and abd > bcd) then
        c, a = a, c;
    elseif (acd > bcd and acd > abd) then
        a, b = b, a;
    end

    ab, ac, bc = b - a, c - a, c - b;

    local right = ac:Cross(ab).unit;
    local up = bc:Cross(right).unit;
    local back = bc.unit;

    local height = math.abs(ab:Dot(up));

    local w1 = wedge:Clone();
    w1.Size = Vector3.new(0, height, math.abs(ab:Dot(back)));
    w1.CFrame = CFrame.fromMatrix((a + b)/2, right, up, back);
    w1.Parent = workspace;

    local w2 = wedge:Clone();
    w2.Size = Vector3.new(0, height, math.abs(ac:Dot(back)));
    w2.CFrame = CFrame.fromMatrix((a + c)/2, -right, up, -back);
    w2.Parent = workspace;

    return w1, w2;
end

local positionGrid = {}

for x = 0, X do
    positionGrid[x] = {}

    for z = 0, Z do
        positionGrid[x][z] = Vector3.new(x*5, math.noise(x/10, z/10) * 10, z*5)
    end
end

for x = 0, X-1 do
    for z = 0, Z-1 do
        local a = positionGrid[x][z]
        local b = positionGrid[x+1][z]
        local c = positionGrid[x][z+1]
        local d = positionGrid[x+1][z+1]

        draw3dTriangle(a, b, c)
        draw3dTriangle(b, c, d)
    end
end