Adding operation for rotating about an axis

2 files changed, 20 insertions, 0 deletions

diff --git a/redist/linmath.c b/redist/linmath.c
index eefcd5f..0e06156 100644
--- a/redist/linmath.c
+++ b/redist/linmath.c
@@ -82,6 +82,25 @@ FLT anglebetween3d( FLT * a, FLT * b )
 	return FLT_ACOS(dot);
 }
 
+// algorithm found here: http://inside.mines.edu/fs_home/gmurray/ArbitraryAxisRotation/
+void rotatearoundaxis(FLT *outvec3, FLT *invec3, FLT *axis, FLT angle)
+{
+	FLT s = FLT_SIN(angle);
+	FLT c = FLT_COS(angle);
+
+	FLT u=axis[0];
+	FLT v=axis[1];
+	FLT w=axis[2];
+
+	FLT x=invec3[0];
+	FLT y=invec3[1];
+	FLT z=invec3[2];
+
+	outvec3[0] = u*(u*x + v*y + w*z)*(1-c)   +   x*c   +   (-w*y + v*z)*s;
+	outvec3[1] = v*(u*x + v*y + w*z)*(1-c)   +   y*c   +   ( w*x - u*z)*s;
+	outvec3[2] = w*(u*x + v*y + w*z)*(1-c)   +   z*c   +   (-v*x + u*y)*s;
+}
+
 /////////////////////////////////////QUATERNIONS//////////////////////////////////////////
 //Originally from Mercury (Copyright (C) 2009 by Joshua Allen, Charles Lohr, Adam Lowman)
 //Under the mit/X11 license.
diff --git a/redist/linmath.h b/redist/linmath.h
index 4e0cb77..6f0bf60 100644
--- a/redist/linmath.h
+++ b/redist/linmath.h
@@ -70,6 +70,7 @@ FLT magnitude3d(const FLT * a );
 
 FLT anglebetween3d( FLT * a, FLT * b );
 
+void rotatearoundaxis(FLT *outvec3, FLT *invec3, FLT *axis, FLT angle);
 //Quaternion things...
 
 void quatsetnone( FLT * q );