Mega Code Archive
Fast trigonometric operations
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//package com.ryanm.droid.rugl.util;
/**
* Fast trigonometric operations
*
* @author Riven
*/
public class Trig {
/**
* I'm sick of casting to float
*/
public static final float PI = (float) Math.PI;
/**
* I'm also sick of multiplying by two
*/
public static final float TWO_PI = 2 * PI;
/**
* Honestly, who has the time to divide by two?
*/
public static final float HALF_PI = PI / 2;
private static final int ATAN2_BITS = 7;
private static final int ATAN2_BITS2 = ATAN2_BITS << 1;
private static final int ATAN2_MASK = ~(-1 << ATAN2_BITS2);
private static final int ATAN2_COUNT = ATAN2_MASK + 1;
private static final int ATAN2_DIM = (int) Math.sqrt(ATAN2_COUNT);
private static final float ATAN2_DIM_MINUS_1 = ATAN2_DIM - 1;
private static final float[] atan2 = new float[ATAN2_COUNT];
private static final int SIN_BITS, SIN_MASK, SIN_COUNT;
private static final float radFull, radToIndex;
private static final float[] sin, cos;
static {
for (int i = 0; i < ATAN2_DIM; i++) {
for (int j = 0; j < ATAN2_DIM; j++) {
float x0 = (float) i / ATAN2_DIM;
float y0 = (float) j / ATAN2_DIM;
atan2[j * ATAN2_DIM + i] = (float) Math.atan2(y0, x0);
}
}
SIN_BITS = 12;
SIN_MASK = ~(-1 << SIN_BITS);
SIN_COUNT = SIN_MASK + 1;
radFull = (float) (Math.PI * 2.0);
radToIndex = SIN_COUNT / radFull;
sin = new float[SIN_COUNT];
cos = new float[SIN_COUNT];
for (int i = 0; i < SIN_COUNT; i++) {
sin[i] = (float) Math.sin((i + 0.5f) / SIN_COUNT * radFull);
cos[i] = (float) Math.cos((i + 0.5f) / SIN_COUNT * radFull);
}
}
/**
* Like {@link Math#sin(double)}, but a lot faster and a bit less accurate
*
* @param rad
* @return sin( rad )
*/
public static final float sin(float rad) {
return sin[(int) (rad * radToIndex) & SIN_MASK];
}
/**
* Like {@link Math#cos(double)}, but a lot faster and a bit less accurate
*
* @param rad
* @return cos( rad )
*/
public static final float cos(float rad) {
return cos[(int) (rad * radToIndex) & SIN_MASK];
}
/**
* @param y
* @param x
* @return the angle to (x,y)
*/
public static final float atan2(float y, float x) {
float add, mul;
if (x < 0.0f) {
if (y < 0.0f) {
x = -x;
y = -y;
mul = 1.0f;
} else {
x = -x;
mul = -1.0f;
}
add = -3.141592653f;
} else {
if (y < 0.0f) {
y = -y;
mul = -1.0f;
} else {
mul = 1.0f;
}
add = 0.0f;
}
float invDiv = ATAN2_DIM_MINUS_1 / (x < y ? y : x);
int xi = (int) (x * invDiv);
int yi = (int) (y * invDiv);
return (atan2[yi * ATAN2_DIM + xi] + add) * mul;
}
/**
* @param degrees
* @return the radians value
*/
public static float toRadians(float degrees) {
return degrees / 180.0f * Trig.PI;
}
/**
* @param radians
* @return the degrees value
*/
public static float toDegrees(float radians) {
return radians * 180.0f / Trig.PI;
}
}
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