public static Matrix3x2 CreateRotation(float radians, Vector2 centerPoint)
{
Matrix3x2 result;
radians = (float)SM.IEEERemainder(radians, SM.PI * 2);
float c, s;
const float epsilon = 0.001f * (float)SM.PI / 180f; // 0.1% of a degree
if (radians > -epsilon && radians < epsilon)
{
// Exact case for zero rotation.
c = 1;
s = 0;
}
else if (radians > SM.PI / 2 - epsilon && radians < SM.PI / 2 + epsilon)
{
// Exact case for 90 degree rotation.
c = 0;
s = 1;
}
else if (radians < -SM.PI + epsilon || radians > SM.PI - epsilon)
{
// Exact case for 180 degree rotation.
c = -1;
s = 0;
}
else if (radians > -SM.PI / 2 - epsilon && radians < -SM.PI / 2 + epsilon)
{
// Exact case for 270 degree rotation.
c = 0;
s = -1;
}
else
{
// Arbitrary rotation.
c = (float)SM.Cos(radians);
s = (float)SM.Sin(radians);
}
float x = centerPoint.X * (1 - c) + centerPoint.Y * s;
float y = centerPoint.Y * (1 - c) - centerPoint.X * s;
// [ c s ]
// [ -s c ]
// [ x y ]
result.M11 = c; result.M12 = s;
result.M21 = -s; result.M22 = c;
result.M31 = x; result.M32 = y;
return(result);
}
private static int Math_Fmod(ILuaState lua)
{
lua.PushNumber(Math.IEEERemainder(lua.L_CheckNumber(1),
lua.L_CheckNumber(2)));
return(1);
}
