From 09a8e5982419b0ff0e37a5737f45beb07174eb5e Mon Sep 17 00:00:00 2001
From: Alessio Quaglino <quaglino@google.com>
Date: Thu, 11 May 2023 04:15:09 -0700
Subject: [PATCH] Create half-edge structure before converting from the C++
 array `userface` to the C array `face`.

PiperOrigin-RevId: 531161474
Change-Id: I77d425f4b5e52b2e41c6c9a2ef187495fefda5b8
---
 src/user/user_mesh.cc | 41 ++++++++++++-----------------------------
 1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/src/user/user_mesh.cc b/src/user/user_mesh.cc
index 90c3f8a8..4c44aecd 100644
--- a/src/user/user_mesh.cc
+++ b/src/user/user_mesh.cc
@@ -280,20 +280,9 @@ void mjCMesh::Compile(int vfs_provider) {
       throw mjCError(this, "face data must be a multiple of 3");
     }
 
-    // copy from user
-    nface = (int)userface.size()/3;
-    face = VecToArray(userface, !file.empty());
-
-    // check vertices exist
-    for (auto vertex_index : userface) {
-      if (vertex_index>=nvert || vertex_index < 0) {
-        throw mjCError(this, "found index in userface that exceeds uservert size.");
-      }
-    }
-
     // create half-edge structure (if mesh was in XML)
     if (useredge.empty()) {
-      for (int i=0; i<nface; i++) {
+      for (int i=0; i<userface.size()/3; i++) {
         int v0 = userface[3*i+0];
         int v1 = userface[3*i+1];
         int v2 = userface[3*i+2];
@@ -307,6 +296,17 @@ void mjCMesh::Compile(int vfs_provider) {
         }
       }
     }
+
+    // copy from user
+    nface = (int)userface.size()/3;
+    face = VecToArray(userface, !file.empty());
+
+    // check vertices exist
+    for (auto vertex_index : userface) {
+      if (vertex_index>=nvert || vertex_index < 0) {
+        throw mjCError(this, "found index in userface that exceeds uservert size.");
+      }
+    }
   }
 
   // check for inconsistent face orientations
@@ -701,23 +701,6 @@ void mjCMesh::LoadOBJ(mjResource* resource) {
         userfacetexcoord.push_back(mesh_index.texcoord_index);
       }
     }
-
-    for (int i = 0; i < face_indices.size(); i += 3) {
-      // add edges
-      const float *v0 = uservert.data() + 3*face_indices[i+0].vertex_index;
-      const float *v1 = uservert.data() + 3*face_indices[i+1].vertex_index;
-      const float *v2 = uservert.data() + 3*face_indices[i+2].vertex_index;
-
-      // only consider edges if the face contribution is significant
-      mjtNum normal[3];
-      if (_triangle(normal, nullptr, v0, v1, v2)>sqrt(mjMINVAL)) {
-        useredge.push_back(std::pair(face_indices[i+0].vertex_index, face_indices[i+1].vertex_index));
-        useredge.push_back(std::pair(face_indices[i+1].vertex_index, face_indices[i+2].vertex_index));
-        useredge.push_back(std::pair(face_indices[i+2].vertex_index, face_indices[i+0].vertex_index));
-      } else {
-        // TODO(b/255525326)
-      }
-    }
   }
 
   // flip the second texcoord