Add vec3.angle_to

modules/vec3.lua

@@ -318,6 +318,11 @@ function vec3.flip_z(a)
 	return vec3.new(a.x, a.y, -a.z)
 end
 
+function vec3.angle_to(a, b)
+	local v = a:normalize():dot(b:normalize())
+	return math.acos(v)
+end
+
 --- Return a boolean showing if a table is or is not a vec3.
 -- @tparam vec3 a Vector to be tested
 -- @treturn boolean is_vec3

spec/vec3_spec.lua

@@ -224,4 +224,10 @@ describe("vec3:", function()
 		temp = temp:flip_z()
 		assert.is.equal(temp, vec3(-1, -2, -3))
 	end)
+
+	-- it("get two 3-vectors angle", function()
+	-- 	local a = vec3(1,2,3)
+	-- 	local b = vec3(3,2,1)
+	-- 	-- assert.is.equal(a:angle_to(b), 1)
+	-- end)
 end)