Merged particle engine into main eAthena branch.

1 files changed, 23 insertions, 0 deletions

diff --git a/src/utils/fastsqrt.h b/src/utils/fastsqrt.h
new file mode 100644
index 00000000..8ba6f8ce
--- /dev/null
+++ b/src/utils/fastsqrt.h
@@ -0,0 +1,23 @@
+/* A very fast function to calculate the approximate inverse square root of a

+ * floating point value and a helper function that uses it for getting the

+ * normal squareroot. For an explanation of the inverse squareroot function

+ * read:

+ * http://www.math.purdue.edu/~clomont/Math/Papers/2003/InvSqrt.pdf

+ *

+ * Unfortunately the original creator of this function seems to be unknown.

+ */

+

+float fastInvSqrt(float x)

+{

+    float xhalf = 0.5f*x;

+    int i = *(int*)&x;

+    i = 0x5f375a86- (i>>1);

+    x = *(float*)&i;

+    x = x*(1.5f-xhalf*x*x);

+    return x;

+}

+

+float fastSqrt(float x)

+{

+    return 1.0f/fastInvSqrt(x);

+}