geom/aabb: add point-aabb distance2

geom/aabb.cpp

@@ -9,6 +9,7 @@
 
 #include "aabb.hpp"
 
+#include "ops.hpp"
 #include "iostream.hpp"
 #include "../coord/iostream.hpp"
 
@@ -35,6 +36,21 @@ aabb<3,float>::vertices (void) const noexcept
 }
 
 
+///////////////////////////////////////////////////////////////////////////////
+/// Returns the squared minimum distance from the AABB to a point.
+template <size_t S, typename T>
+T cruft::geom::distance2 (aabb<S,T> a, point<S,T> b)
+{
+    auto const clamped = cruft::max (
+        a.lo - b,
+        vector<S,T> (0),
+        b - a.hi
+    );
+
+    return sum (clamped * clamped);
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 namespace cruft::debug {
     template <size_t S, typename T>
@@ -60,8 +76,9 @@ cruft::geom::operator<< (std::ostream &os, cruft::geom::aabb<S,T> b)
 #define INSTANTIATE_S_T(S,T)                             \
 namespace cruft::geom { template struct aabb<S,T>; }      \
 template bool cruft::debug::is_valid (const aabb<S,T>&);  \
-template std::ostream& cruft::geom::operator<< (std::ostream&, aabb<S,T>);
-
+template std::ostream& cruft::geom::operator<< (std::ostream&, aabb<S,T>); \
+template T cruft::geom::distance2 (point<S,T>, aabb<S,T>); \
+template T cruft::geom::distance2 (aabb<S,T>, point<S,T>);
 #define INSTANTIATE(T)  \
 INSTANTIATE_S_T(2,T)    \
 INSTANTIATE_S_T(3,T)

geom/aabb.hpp

@@ -192,6 +192,21 @@ namespace cruft::geom {
     {
         return a.inclusive (b);
     }
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// Returns the squared minimum distance from the AABB to a point.
+    template <size_t S, typename T>
+    T distance2 (aabb<S,T> a, point<S,T> b);
+
+
+    //-------------------------------------------------------------------------
+    template <size_t S, typename T>
+    T
+    distance2 (point<S,T> a, aabb<S,T> b)
+    {
+        return distance2 (b, a);
+    }
 }