1 files changed, 26 insertions, 0 deletions
diff --git a/vector.c b/vector.c
new file mode 100644
index 0000000..d0e304a
--- /dev/null
+++ b/vector.c
@@ -0,0 +1,26 @@
+#include "vector.h"
+#include <math.h>
+
+void normalize(double *a)
+{
+    double c;
+    c = NORM(a);
+    DIV(a,c);
+}
+
+void rotate(double *dest, double *v, double *n, double phi)
+{
+    /* Rotate the vector `v` through an angle `phi` about the axis `n`. */
+    double temp[3], cos_theta;
+
+    cos_theta = cos(phi);
+
+    COPY(dest,v);
+    MUL(dest,cos_theta);
+    CROSS(temp,n,v);
+    MUL(temp,sin(phi));
+    ADD(dest,dest,temp);
+    COPY(temp,n);
+    MUL(temp,DOT(n,v)*(1-cos_theta));
+    ADD(dest,dest,temp);
+}