3D Triangle

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

while true do
    local a = workspace.A.Position
    local b = workspace.B.Position
    local c = workspace.C.Position

    local wedgeA, wedgeB = draw3dTriangle(a, b, c)

    wait()

    wedgeA:Destroy()
    wedgeB:Destroy()
end