point/vector: give homog a default dimensionality

point.hpp

@@ -39,7 +39,7 @@ namespace util {
 
         /// expand point to use homogenous coordinates of a higher dimension.
         /// ie, fill with (0,..,0,1)
-        template <size_t D>
+        template <size_t D = 4>
         point<D,T>
         homog (void) const
         {

vector.hpp

@@ -35,7 +35,8 @@ namespace util {
         using coord::base<S,T,vector<S,T>>::base;
 
         // representations
-        template <size_t D> vector<D,T> homog (void) const
+        template <size_t D = 4>
+        vector<D,T> homog (void) const
         {
             static_assert (D > S, "reducing size loses data");
             return (*this).template redim<D> (0.f);