corrected some simple warning and avoided collapse of edges of triangular faces for polygons

vcg/complex/algorithms/parametrization/tangent_field_operators.h

@@ -624,7 +624,7 @@ public:
         do
         {
             std::vector<int> new_queue;
-            for (int i=0; i<queue.size(); i++)
+            for (size_t i=0; i<queue.size(); i++)
             {
                 FaceType *f0=&(mesh.face[queue[i]]);
                 assert(!f0->IsD());

vcg/complex/algorithms/polygonal_algorithms.h

@@ -1181,6 +1181,14 @@ public:
             for (int j=0;j<poly_m.face[i].VN();j++)
                 valenceVertH[poly_m.face[i].V(j)]++;
 
+        //cannot collapse triangular vertices otherwise will collapse to a segment
+        for (size_t i=0;i<poly_m.face.size();i++)
+        {
+            if (poly_m.face[i].VN()>3)continue;
+            for (int j=0;j<poly_m.face[i].VN();j++)
+                valenceVertH[poly_m.face[i].V(j)]=3;
+        }
+
         //then re-elaborate the faces
         for (size_t i=0;i<poly_m.face.size();i++)
         {

vcg/container/simple_temporary_data.h

@@ -82,7 +82,7 @@ public:
     void resize(size_t sz)
     {
         int oldDatasize = datasize;
-        if (sz <= oldDatasize)
+        if ((int)sz <= oldDatasize)
             return;
         if (sz > datareserve)
             reserve(sz);