Math.atan2() is very convenient, yet very slow.
A lookup table will be roughly 8x faster.
You lose accuracy, but heck, that's obvious.
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| public static final float atan2Deg(float y, float x)
{
return FastMath.atan2(y, x) * DEG;
}
public static final float atan2DegStrict(float y, float x)
{
return (float) Math.atan2(y, x) * DEG;
}
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;
}
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];
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);
}
}
} |
