add rotation to c31 hexagons

needs some cleanup but it's pretty efficient, at least

1 files changed, 6 insertions, 0 deletions

diff --git a/math.cginc b/math.cginc
index 15d02eb..ee70495 100755
--- a/math.cginc
+++ b/math.cginc
@@ -67,6 +67,12 @@ float3 rotate_vector(float3 v, float4 q)
   return v + q.w * t + cross(q.xyz, t);
 }
 
+float4 get_quaternion(float3 axis_normal, float theta) {
+  float sint2, cost2;
+  sincos(theta*0.5, sint2, cost2);
+  return float4(axis_normal * sint2, cost2);
+}
+
 // Cartesian to packed cube hexagonal coordinates.
 // Stores (q + r, q, r), where the article's cube coordinates satisfy
 // q + r + s = 0 and s = -(q + r).