gered/Blarg.GameFramework
Archived
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity

add fast inverse sqrt method

Browse source
This commit is contained in:
Gered 2013-08-24 20:08:26 -04:00
parent 70acec6b0f
commit d008ce4875
1 changed files with 30 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

30
Blarg.GameFramework/Math/MathHelpers.cs
View file

@ -1,4 +1,5 @@
using System; using System;
using System.Runtime.InteropServices;
namespace Blarg.GameFramework namespace Blarg.GameFramework
{ {
@ -198,6 +199,24 @@ namespace Blarg.GameFramework
return degrees * MathConstants.PiOver180; return degrees * MathConstants.PiOver180;
} }
/// <summary>
/// A fast method for calculating the inverse square root of a nunmber.
/// </summary>
/// <returns>The inverse square root of the given number.</returns>
/// <param name="x">The value to get the inverse square root of.</param>
/// <remarks>Copy of the famous method from the Quake 3 source.</remarks>
public static float FastInverseSqrt(float x)
{
FloatIntUnion convert;
convert.i = 0;
convert.x = x;
float xhalf = 0.5f * x;
convert.i = 0x5f3759df - (convert.i >> 1);
x = convert.x;
x = x * (1.5f - xhalf * x * x);
return x;
}
/// <summary> /// <summary>
/// Checks two floats for equality using a defined "tolerance" to account /// Checks two floats for equality using a defined "tolerance" to account
/// for floating point rounding errors, etc. /// for floating point rounding errors, etc.
@ -311,5 +330,16 @@ namespace Blarg.GameFramework
float n = Clamp(t, 0.0f, 1.0f); float n = Clamp(t, 0.0f, 1.0f);
return Lerp(low, high, (n * n) * (3.0f - (2.0f * n))); return Lerp(low, high, (n * n) * (3.0f - (2.0f * n)));
} }
// this is to allow access to raw float bits
[StructLayout(LayoutKind.Explicit)]
public struct FloatIntUnion
{
[FieldOffset(0)]
public float x;
[FieldOffset(0)]
public int i;
}
} }
} }