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Blazingly fast Minecraft world manipulation for artists, builders and everyone else.

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/*
 * WorldEdit, a Minecraft world manipulation toolkit
 * Copyright (C) sk89q 
 * 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 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package com.sk89q.worldedit.math.geom;

import com.sk89q.worldedit.math.BlockVector2;
import com.sk89q.worldedit.math.Vector2;

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 BlockVector2} which resemble the shape as a polygon
     */
    public static List polygonizeCylinder(BlockVector2 center, Vector2 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 points = new ArrayList<>(nPoints);
        for (int i = 0; i < nPoints; ++i) {
            double angle = i * (2.0 * Math.PI) / nPoints;
            final Vector2 pos = Vector2.at(Math.cos(angle), Math.sin(angle));
            final BlockVector2 blockVector2D = pos.multiply(radius).toBlockPoint().add(center);
            points.add(blockVector2D);
        }

        return points;
    }

}