fast Atan - CSharp System

CSharp examples for System:Math Geometry

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Description

fast Atan

Demo Code

/* //from w w  w .  ja  v a 2s .c o  m
 * PROJECT: NyARToolkit
 * --------------------------------------------------------------------------------
 * The NyARToolkit is Java edition ARToolKit class library.
 *  Copyright (C)2016 Ryo Iizuka
 * 
 * NyARToolkit is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as publishe
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * NyARToolkit 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/>.
 * 
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent modules, and to
 * copy and distribute the resulting executable under terms of your choice,
 * provided that you also meet, for each linked independent module, the terms and
 * conditions of the license of that module. An independent module is a module
 * which is neither derived from nor based on this library. If you modify this
 * library, you may extend this exception to your version of the library, but you
 * are not obligated to do so. If you do not wish to do so, delete this exception
 * statement from your version.
 * 
 */
using System;

public class Main{
        public static double fastAtan2(double y, double x)
        {
            if (x == 0.0f)
            {
                if (y > 0.0f)
                {
                    return (Math.PI / 2);
                }
                if (y < 0.0f)
                {
                    return -(Math.PI / 2);
                }
                return 0.0f;
            }
            double atan;
            double z = y / x;
            if (z * z < 1.0f)
            {
                atan = z / (1.0f + 0.28f * z * z);
                if (x < 0.0f)
                {
                    if (y < 0.0f)
                    {
                        return atan - Math.PI;
                    }
                    return atan + Math.PI;
                }
            }
            else
            {
                atan = (Math.PI / 2) - z / (z * z + 0.28f);
                if (y < 0.0f)
                {
                    return atan - Math.PI;
                }
            }
            return atan;
        }
}

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