Mesh: Parallelize bounding box calculation (WIP)

This replaces the single-threaded calculation of mesh min and max
positions with a `parallel_reduce` loop. Since the bounding box
of a mesh is retrieved quite often (at the end of each evaluation,
currently 2(?!) times when leaving edit mode, etc.), this makes for a
quite noticeable speedup actually.

On my Ryzen 3700x and a 4.2 million vertex mesh, I observed
a 4.4x performance increase, from 14 ms to 4.4 ms.

I added some methods to `float3` so they would be inlined, but
they're also a nice addition, since they're used often anyway.

Differential Revision: https://developer.blender.org/D13572

1 files changed, 16 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_float3.hh b/source/blender/blenlib/BLI_float3.hh
index 6ee0c4b973b..765f524fb31 100644
--- a/source/blender/blenlib/BLI_float3.hh
+++ b/source/blender/blenlib/BLI_float3.hh
@@ -228,6 +228,22 @@ struct float3 {
     return result;
   }
 
+  static float3 min(const float3 &a, const float3 &b)
+  {
+    return {a.x < b.x ? a.x : b.x, a.y < b.y ? a.y : b.y, a.z < b.z ? a.z : b.z};
+  }
+
+  static float3 max(const float3 &a, const float3 &b)
+  {
+    return {a.x > b.x ? a.x : b.x, a.y > b.y ? a.y : b.y, a.z > b.z ? a.z : b.z};
+  }
+
+  static void min_max(const float3 &vector, float3 &min, float3 &max)
+  {
+    min = float3::min(vector, min);
+    max = float3::max(vector, max);
+  }
+
   static float3 safe_divide(const float3 &a, const float b)
   {
     return (b != 0.0f) ? a / b : float3(0.0f);