spine-runtimes/spine-csharp/src/MathUtils.cs

/******************************************************************************
 * Spine Runtimes Software License
 * Version 2.3
 * 
 * Copyright (c) 2013-2015, Esoteric Software
 * All rights reserved.
 * 
 * You are granted a perpetual, non-exclusive, non-sublicensable and
 * non-transferable license to use, install, execute and perform the Spine
 * Runtimes Software (the "Software") and derivative works solely for personal
 * or internal use. Without the written permission of Esoteric Software (see
 * Section 2 of the Spine Software License Agreement), you may not (a) modify,
 * translate, adapt or otherwise create derivative works, improvements of the
 * Software or develop new applications using the Software or (b) remove,
 * delete, alter or obscure any trademarks or any copyright, trademark, patent
 * or other intellectual property or proprietary rights notices on or in the
 * Software, including any copy thereof. Redistributions in binary or source
 * form must include this license and terms.
 * 
 * THIS SOFTWARE IS PROVIDED BY ESOTERIC SOFTWARE "AS IS" AND ANY EXPRESS OR
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 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

using System;

namespace Spine {
	public static class MathUtils {
		public const float PI = 3.1415927f;
		public const float PI2 = PI * 2;
		public const float radDeg = 180f / PI;
		public const float degRad = PI / 180;

		const int SIN_BITS = 14; // 16KB. Adjust for accuracy.
		const int SIN_MASK = ~(-1 << SIN_BITS);
		const int SIN_COUNT = SIN_MASK + 1;
		const float radFull = PI * 2;
		const float degFull = 360;
		const float radToIndex = SIN_COUNT / radFull;
		const float degToIndex = SIN_COUNT / degFull;
		static float[] sin = new float[SIN_COUNT];

		static MathUtils () {
			for (int i = 0; i < SIN_COUNT; i++)
				sin[i] = (float)Math.Sin((i + 0.5f) / SIN_COUNT * radFull);
			for (int i = 0; i < 360; i += 90)
				sin[(int)(i * degToIndex) & SIN_MASK] = (float)Math.Sin(i * degRad);
		}

		/// <summary>Returns the sine in radians from a lookup table.</summary>
		static public float Sin (float radians) {
			return sin[(int)(radians * radToIndex) & SIN_MASK];
		}

		/// <summary>Returns the cosine in radians from a lookup table.</summary>
		static public float Cos (float radians) {
			return sin[(int)((radians + PI / 2) * radToIndex) & SIN_MASK];
		}
			
		/// <summary>Returns the sine in radians from a lookup table.</summary>
		static public float SinDeg (float degrees) {
			return sin[(int)(degrees * degToIndex) & SIN_MASK];
		}
			
		/// <summary>Returns the cosine in radians from a lookup table.</summary>
		static public float CosDeg (float degrees) {
			return sin[(int)((degrees + 90) * degToIndex) & SIN_MASK];
		}

		/// <summary>Returns atan2 in radians, faster but less accurate than Math.Atan2. Average error of 0.00231 radians (0.1323
		/// degrees), largest error of 0.00488 radians (0.2796 degrees).</summary>
		static public float Atan2 (float y, float x) {
			if (x == 0f) {
				if (y > 0f) return PI / 2;
				if (y == 0f) return 0f;
				return -PI / 2;
			}
			float atan, z = y / x;
			if (Math.Abs(z) < 1f) {
				atan = z / (1f + 0.28f * z * z);
				if (x < 0f) return atan + (y < 0f ? -PI : PI);
				return atan;
			}
			atan = PI / 2 - z / (z * z + 0.28f);
			return y < 0f ? atan - PI : atan;
		}

		static public float Clamp (float value, float min, float max) {
			if (value < min) return min;
			if (value > max) return max;
			return value;
		}
	}
}