diff --git a/README.md b/README.md
index 7672478..0c5f542 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,8 @@ npm i git://github.com/ykob/glsl-util.git
 ```
 
 ## convertHsvToRgb and convertRgbToHsv
-this is the function that convetts RGB to HSV. or is its opposite.
+
+this function converts RGB to HSV. or is its opposite.
 
 ### Quote source
 
@@ -29,3 +30,14 @@ http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl
 ```
 #pragma glslify: random = require(glsl-util/random);
 ```
+
+## polar
+
+this function calculates polar coordinates.
+
+### usage
+
+```
+#pragma glslify: polar = require(glsl-util/polar);
+vec3 p = polar(float radian1, float radian2, float radius);
+```
diff --git a/polar.glsl b/polar.glsl
new file mode 100644
index 0000000..d394cac
--- /dev/null
+++ b/polar.glsl
@@ -0,0 +1,8 @@
+vec3 polar(float radian1, float radian2, float radius) {
+  return vec3(
+    cos(radian1) * cos(radian2) * radius,
+    sin(radian1) * radius,
+    cos(radian1) * sin(radian2) * radius,
+  )
+}
+#pragma glslify: export(polar)