From 88f7e7a38d7b7fa0736b7fcab0e0271182d63144 Mon Sep 17 00:00:00 2001
From: GaborFarkas <raandal73@gmail.com>
Date: Thu, 8 Sep 2016 10:04:36 +0200
Subject: [PATCH] Utilities for polygon renderer

---
 src/ol/render/webgl/webgl.js | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/ol/render/webgl/webgl.js b/src/ol/render/webgl/webgl.js
index 498ff2d72f..dbaafc7e77 100644
--- a/src/ol/render/webgl/webgl.js
+++ b/src/ol/render/webgl/webgl.js
@@ -59,3 +59,24 @@ ol.render.webgl.lineStringInstruction = {
   MITER_BOTTOM: 19,
   MITER_TOP: 23
 };
+
+/**
+ * Calcualtes the orientation of a triangle based on the determinant method.
+ * @param {number} x1 First X coordinate.
+ * @param {number} y1 First Y coordinate.
+ * @param {number} x2 Second X coordinate.
+ * @param {number} y2 Second Y coordinate.
+ * @param {number} x3 Third X coordinate.
+ * @param {number} y3 Third Y coordinate.
+ * @return {boolean|undefined} Triangle is clockwise.
+ */
+ol.render.webgl.triangleIsCounterClockwise = function(x1, y1, x2, y2, x3, y3) {
+  var area = (x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1);
+  return area === 0 ? undefined : area > 0;
+};
+
+/**
+ * @const
+ * @type {number}
+ */
+ol.render.webgl.EPSILON = Number.EPSILON || 2.220446049250313e-16;