// Arc Tangent (inverse tangent)
// Uses GBA implementation: http://www.coranac.com/documents/arctangent/
public static FInt Atan(FInt dx, FInt dy)
{
if (dx.Value() == 0)
{
if (dy.Value() >= 0)
{
return new FInt(0.5) * PI;
}
else
{
return new FInt(1.5) * PI;
}
}
if (dy.Value() == 0)
{
if (dx.Value() > 0)
{
return 0L;
}
else
{
return PI;
}
}
if (dx.Value() < 0)
{
if (dy.Value() < 0)
{
return PI + Atan(-dx, -dy);
}
else
{
return PI - Atan(-dx, dy);
}
}
else
{
if (dy.Value() < 0)
{
return 2 * PI - Atan(dx, -dy);
}
}
bool swapAxes = false;
if (dy > dx)
{
FInt tmp = dy;
dy = dx;
dx = tmp;
swapAxes = true;
}
long t = (dy.Value() << FLOATING_BITS) / dx.Value();
long t2 = -(t * t) >> FLOATING_BITS;
long t4 = (t2 * t2) >> FLOATING_BITS;
long t6 = (t4 * t2) >> FLOATING_BITS;
long t8 = (t4 * t4) >> FLOATING_BITS;
long t10 = (t6 * t4) >> FLOATING_BITS;
long t12 = (t6 * t6) >> FLOATING_BITS;
long t14 = (t8 * t6) >> FLOATING_BITS;
FInt x = new FInt(
((65536L * t) >> FLOATING_BITS) +
((((21845L * t) >> FLOATING_BITS) * t2) >> FLOATING_BITS) +
((((13107L * t) >> FLOATING_BITS) * t4) >> FLOATING_BITS) +
((((9102L * t) >> FLOATING_BITS) * t6) >> FLOATING_BITS) +
((((6317L * t) >> FLOATING_BITS) * t8) >> FLOATING_BITS) +
((((3664L * t) >> FLOATING_BITS) * t10) >> FLOATING_BITS) +
((((1432L * t) >> FLOATING_BITS) * t12) >> FLOATING_BITS) +
((((266L * t) >> FLOATING_BITS) * t14) >> FLOATING_BITS));
if (swapAxes)
{
return PI / 2 - x;
}
return x;
}
public static FInt Sqrt(FInt a)
{
if (a.Value() == 0L)
{
return a;
}
FInt x = 1L;
for (int i = 0; i < 64; i++)
{
x = (x + a / x) / 2;
}
return x;
}
public static FInt Max(FInt a, FInt b)
{
long x = a.Value();
long y = b.Value();
return (x >= y) ? a : b;
}
public static FInt Min(FInt a, FInt b)
{
long x = a.Value();
long y = b.Value();
return (x >= y) ? b : a;
}
public FInt(FInt x)
{
value = x.Value();
floatValue = (float)(value / FSHIFT);
}
