Modified IsConvex helper to handle lines of collinear points

Signed-off-by: Martin Evans <martindevans@gmail.com>
TomGillen · Apr 8, 2014 · d2d3ac2 · d2d3ac2
1 parent 39c3bcb
commit d2d3ac2
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Showing 2 changed files with 13 additions and 6 deletions.
diff --git a/Myre/Myre/Extensions/Vector2Extensions.cs b/Myre/Myre/Extensions/Vector2Extensions.cs
@@ -88,6 +88,7 @@ public static float Area(this Vector2[] v)
         public static bool IsConvex(this Vector2[] v)
         {
             int sign = 0;
+            bool first = true;
             for (int i = 0; i < v.Length; i++)
             {
                 var p = v[i];
@@ -97,12 +98,18 @@ public static bool IsConvex(this Vector2[] v)
                 var d1 = p1 - p;
                 var d2 = p2 - p1;
 
-                var zcrossproduct = d1.X * d2.Y - d1.Y * d2.X;
+                var crossProductSign = Math.Sign(d1.X * d2.Y - d1.Y * d2.X);
 
-                if (i == 0)
-                    sign = Math.Sign(zcrossproduct);
-                else if (Math.Sign(zcrossproduct) != sign)
-                    return false;
+                if (crossProductSign != 0)
+                {
+                    if (first)
+                    {
+                        sign = crossProductSign;
+                        first = false;
+                    }
+                    else if (crossProductSign != sign)
+                        return false;
+                }
             }
 
             return true;

diff --git a/Myre/Myre/Properties/AssemblyInfo.cs b/Myre/Myre/Properties/AssemblyInfo.cs
@@ -27,6 +27,6 @@
 //      Build Number
 //      Revision
 //
-[assembly: AssemblyVersion("1.2.0")]
+[assembly: AssemblyVersion("1.2.1")]
 
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("MyreTests")]