fix: type of files that can be supported

src/morphist_viewer.cpp

 #include "morphist_viewer.hpp"
-#include "nfd.hpp"
 #include "sdf.hpp"
 #include "marching_cubes.h"
 
+#include <filesystem>
 #include <imgui.h>
 #include <pmp/surface_mesh.h>
 #include <pmp/io/io.h>
@@ -29,9 +29,7 @@ void MorphistViewer::keyboard(int key, int scancode, int action, int mods)
 
 void MorphistViewer::process_imgui()
 {
-    NFD::Guard nfdGuard;
-    NFD::UniquePath outPath;
-    nfdfilteritem_t filterItem[1] = {{"3D Objects", "obj"}};
+    
 
     ImGui::Spacing();
 
@@ -46,7 +44,7 @@ void MorphistViewer::process_imgui()
             nfdresult_t result = NFD::OpenDialog(outPath, filterItem, 1);
             if (result == NFD_OKAY) {
                 pmp::read(this->mesh1, outPath.get());
-                this->mesh1_name = outPath.get();
+                this->mesh1_name = std::filesystem::path( outPath.get()).filename();
             }
         }
         ImGui::Text("%s", this->mesh1_name.c_str());
@@ -60,7 +58,7 @@ void MorphistViewer::process_imgui()
             nfdresult_t result = NFD::OpenDialog(outPath, filterItem, 1);
             if (result == NFD_OKAY) {
                 pmp::read(this->mesh2, outPath.get());
-                this->mesh2_name = outPath.get();
+                this->mesh2_name = std::filesystem::path( outPath.get()).filename();
             }
         }
         ImGui::Text("%s", this->mesh2_name.c_str());

src/morphist_viewer.hpp

 #pragma once
 
+#include "nfd.hpp"
 #include "sdf.hpp"
 #include <pmp/visualization/mesh_viewer.h>
 
@@ -26,6 +27,9 @@ protected:
     void process_imgui() override;
 
 private:
+    NFD::Guard nfdGuard;
+    NFD::UniquePath outPath;
+    nfdfilteritem_t const filterItem[1] = {{"3D Objects", "obj,off,stl"}};
     bool is_baking = false;
     bool is_mesh_baked = false;
     bool is_morph_playing = false;