Added preserve_border argument to lossless method.

README.rst

@@ -98,13 +98,14 @@ Parameters of the **`simplify\_mesh\_lossless`** method that can be tuned.
     Maximal error after which a vertex is not deleted.
 -  **max\_iterations**
     Maximum number of iterations.
+-  **preserve\_border**
+    Flag for preserving the vertices situated on open borders. Applies the method described in `this issue <https://github.com/sp4cerat/Fast-Quadric-Mesh-Simplification/issues/14>`__.
 
 Note
 ~~~~
 
 - The **`simplify\_mesh\_lossless`** method is different from the **`simplify\_mesh`** method with the lossless flag enabled, and should be prefered when quality is the aim and not a precise number of target triangles.
 - Tests have shown that the **threshold\_lossless** argument has little to no influence on the reduction of the meshes.
-- On the other hand, only the basic algorithm has the option (yet) to preserve open borders.
 
 
 Implications of the parameters for the threshold growth rate :

pyfqmr/Simplify.h

@@ -454,7 +454,7 @@ namespace Simplify
     compact_mesh();
   } //simplify_mesh()
 
-  void simplify_mesh_lossless(void (*log)(char*, int)=NULL, double epsilon=1e-3, int max_iterations = 9999)
+  void simplify_mesh_lossless(void (*log)(char*, int)=NULL, double epsilon=1e-3, int max_iterations = 9999, bool preserve_border = false)
   {
     // init
     loopi(0,triangles.size())
@@ -499,8 +499,12 @@ namespace Simplify
           int i0=t.v[ j     ]; Vertex &v0 = vertices[i0];
           int i1=t.v[(j+1)%3]; Vertex &v1 = vertices[i1];
 
-          // Border check
-          if(v0.border != v1.border)  continue;
+          // Border check //Added preserve_border method from issue 14 for lossless
+          if(preserve_border){
+            if (v0.border || v1.border) continue; // should keep border vertices
+          }
+          else
+            if (v0.border != v1.border)  continue; // base behaviour
 
           // Compute vertex to collapse to
           vec3f p;

pyfqmr/Simplify.pyx

@@ -23,7 +23,7 @@ cdef extern from "Simplify.h" namespace "Simplify" :
     void simplify_mesh( int target_count, int update_rate, double aggressiveness,
                         void (*log)(char*, int), int max_iterations,double alpha, int K,
                         bool lossless, double threshold_lossless, bool preserve_border)
-    void simplify_mesh_lossless(void (*log)(char*, int), double epsilon, int max_iterations)
+    void simplify_mesh_lossless(void (*log)(char*, int), double epsilon, int max_iterations, bool preserve_border)
     void setMeshFromExt(vector[vector[double]] vertices, vector[vector[int]] faces)
     vector[vector[int]] getFaces()
     vector[vector[double]] getVertices()
@@ -107,7 +107,12 @@ cdef class Simplify :
         self.triangles_cpp.clear()
         self.vertices_cpp.clear()
         self.normals_cpp.clear()
+
         # Here we will need some checks, just to make sure the right objets are passed
+        # Maybe other checks like max(faces)==len(vertices) could be added
+        if not np.issubdtype(faces.dtype, np.integer):
+            raise TypeError("faces array must be of integer type")
+
         self.faces_mv = faces.astype(dtype="int32", subok=False, copy=False)
         self.vertices_mv = vertices.astype(dtype="float64", subok=False, copy=False)
         self.triangles_cpp = setFacesNogil(self.faces_mv, self.triangles_cpp)
@@ -171,7 +176,7 @@ cdef class Simplify :
                 round(t_end-t_start,4), N_start, N_end)
             )
 
-    cpdef void simplify_mesh_lossless(self, bool verbose = True, double epsilon=1e-3, int max_iterations=9999):
+    cpdef void simplify_mesh_lossless(self, bool verbose = True, double epsilon=1e-3, int max_iterations=9999, bool preserve_border = False):
         """Simplify mesh using lossless method
 
             Parameters
@@ -191,7 +196,7 @@ cdef class Simplify :
 
         N_start = self.faces_mv.shape[0]
         t_start = _time()
-        simplify_mesh_lossless(log, epsilon, max_iterations)
+        simplify_mesh_lossless(log, epsilon, max_iterations, preserve_border)
         t_end = _time()
         N_end = getFaces().size()
 
@@ -205,7 +210,7 @@ cdef class Simplify :
 @cython.boundscheck(False)
 @cython.wraparound(False)  # turn off negative index wrapping for entire function
 @cython.nonecheck(False)
-cdef vector[vector[double]] setVerticesNogil(double[:,:] vertices, vector[vector[double]] vector_vertices )nogil:
+cdef vector[vector[double]] setVerticesNogil(double[:,:] vertices, vector[vector[double]] vector_vertices )nogil noexcept:
     """nogil function for filling the vector of vertices, "vector_vertices",
     with the data found in the memory view of the array "vertices"
     """
@@ -224,7 +229,7 @@ cdef vector[vector[double]] setVerticesNogil(double[:,:] vertices, vector[vector
 @cython.boundscheck(False)
 @cython.wraparound(False)  # turn off negative index wrapping for entire function
 @cython.nonecheck(False)
-cdef vector[vector[int]] setFacesNogil(int[:,:] faces, vector[vector[int]] vector_faces )nogil:
+cdef vector[vector[int]] setFacesNogil(int[:,:] faces, vector[vector[int]] vector_faces )nogil noexcept:
     """nogil function for filling the vector of faces, "vector_faces",
     with the data found in the memory view of the array "faces"
     """

tests/test_simplify.py

@@ -25,7 +25,7 @@ def test_example():
 
 def test_empty():
     verts = np.zeros((0,3), dtype=np.float32)
-    faces = np.zeros((0,3), dtype=np.float32)
+    faces = np.zeros((0,3), dtype=np.int32)
 
     simp = pyfqmr.Simplify()
     simp.setMesh(verts, faces)
@@ -50,7 +50,7 @@ def test_example_lossless():
 
 def test_empty_lossless():
     verts = np.zeros((0,3), dtype=np.float32)
-    faces = np.zeros((0,3), dtype=np.float32)
+    faces = np.zeros((0,3), dtype=np.int32)
 
     simp = pyfqmr.Simplify()
     simp.setMesh(verts, faces)