Merge pull request #287

src/main/java/com/sk89q/worldedit/math/geom/Polygons.java

@@ -0,0 +1,64 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.math.geom;
+
+import com.sk89q.worldedit.BlockVector2D;
+import com.sk89q.worldedit.Vector2D;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Helper method for anything related to polygons.
+ */
+public final class Polygons {
+
+    private Polygons() {
+        
+    }
+
+    /**
+     * Calculates the polygon shape of a cylinder which can then be used for e.g. intersection detection.
+     * 
+     * @param center the center point of the cylinder
+     * @param radius the radius of the cylinder
+     * @param maxPoints max points to be used for the calculation
+     * @return a list of {@link BlockVector2D} which resemble the shape as a polygon
+     */
+    public static List<BlockVector2D> polygonizeCylinder(Vector2D center, Vector2D radius, int maxPoints) {
+        int nPoints = (int) Math.ceil(Math.PI*radius.length());
+
+        // These strange semantics for maxPoints are copied from the selectSecondary method.
+        if (maxPoints >= 0 && nPoints >= maxPoints) {
+            nPoints = maxPoints - 1;
+        }
+
+        final List<BlockVector2D> points = new ArrayList<BlockVector2D>(nPoints);
+        for (int i = 0; i < nPoints; ++i) {
+            double angle = i * (2.0 * Math.PI) / nPoints;
+            final Vector2D pos = new Vector2D(Math.cos(angle), Math.sin(angle));
+            final BlockVector2D blockVector2D = pos.multiply(radius).add(center).toBlockVector2D();
+            points.add(blockVector2D);
+        }
+
+        return points;
+    }
+    
+}