1 files changed, 24 insertions, 0 deletions
diff --git a/src/rotate.h b/src/rotate.h
new file mode 100644
index 0000000..52d6d6a
--- /dev/null
+++ b/src/rotate.h
@@ -0,0 +1,24 @@
+#ifndef __ROTATE_H__
+#define __ROTATE_H__
+
+__device__ const Matrix IDENTITY_MATRIX = {1,0,0,0,1,0,0,0,1};
+__device__ const Matrix ZERO_MATRIX = {0,0,0,0,0,0,0,0,0};
+
+__device__ __host__ Matrix make_rotation_matrix(float phi, const float3 &n)
+{
+	/* rotate points counterclockwise, when looking towards +infinity,
+	   through an angle `phi` about the axis `n`. */
+
+	float cos_phi = cosf(phi);
+	float sin_phi = sinf(phi);
+
+	return IDENTITY_MATRIX*cos_phi + (1-cos_phi)*outer(n,n) +
+		sin_phi*make_matrix(0,n.z,-n.y,-n.z,0,n.x,n.y,-n.x,0);
+}
+
+__device__ __host__ float3 rotate(const float3 &a, float phi, const float3 &n)
+{
+	return make_rotation_matrix(phi,n)*a;
+}
+
+#endif