Allow loading obj meshes

2025-01-20 11:09:18 +00:00
parent 61973a33c9
commit 36cbef50b7
3 changed files with 112 additions and 10 deletions
@@ -0,0 +1,94 @@
+// Copyright 2019 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+using System;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Text;
+using UnityEngine;
+
+namespace Mujoco {
+
+  /// <summary>
+  /// Scale vertex data manually line by line. We skip normals. Parameter vertex points
+  /// (`vp`) was unclear to me how to properly scale them, if you use them and notice an
+  /// issue please report it.
+  /// </summary>
+  public static class ObjMeshImportUtility {
+    private static Vector3 ToXZY(float x, float y, float z) => new Vector3(x, z, y);
+
+    public static void CopyAndScaleOBJFile(string sourceFilePath, string targetFilePath,
+        Vector3 scale, bool flipFaces=false) {
+      // OBJ files are human readable
+      string[] lines = File.ReadAllLines(sourceFilePath);
+      StringBuilder outputBuilder = new StringBuilder();
+      // Culture info for consistent decimal point handling
+      CultureInfo invariantCulture = CultureInfo.InvariantCulture;
+
+      scale = ToXZY(scale.x, scale.y, scale.z);
+      foreach (string line in lines) {
+        if (line.StartsWith("v ")) // Vertex line
+        {
+          // Split the line into components
+          string[] parts = line.Split(' ');
+          if (parts.Length >= 4) {
+            // Scale the vertex
+            float x = -float.Parse(parts[1], invariantCulture) * scale.x;
+            float y = float.Parse(parts[2], invariantCulture) * scale.y;
+            float z = float.Parse(parts[3], invariantCulture) * scale.z;
+
+            var swizzled = ToXZY(x, y, z);
+            outputBuilder.AppendLine(
+                $"v {swizzled.x.ToString(invariantCulture)} {swizzled.y.ToString(invariantCulture)} {swizzled.z.ToString(invariantCulture)}");
+          }
+        } else if (line.StartsWith("vn ")) {
+          string[] parts = line.Split(' ');
+          if (parts.Length >= 4) {
+            float x = -float.Parse(parts[1], invariantCulture);
+            float y = float.Parse(parts[2], invariantCulture);
+            float z = float.Parse(parts[3], invariantCulture);
+
+            var swizzled = ToXZY(x, y, z);
+            outputBuilder.AppendLine(
+                $"vn {swizzled.x.ToString(invariantCulture)} {swizzled.y.ToString(invariantCulture)} {swizzled.z.ToString(invariantCulture)}");
+          }
+        } else if (line.StartsWith("f ") && flipFaces) {
+          string[] parts = line.Split(' ');
+          if (parts.Length >= 4) {
+            outputBuilder.Append(parts[0] + " ");
+
+            // Apply same vertex order as STL parser: [0,2,1]
+            var face = parts.Skip(1).ToArray();
+            if (face.Length >= 3) {
+              outputBuilder.Append(face[0] + " ");  // vertex 0
+              outputBuilder.Append(face[2] + " ");  // vertex 2
+              outputBuilder.Append(face[1]);        // vertex 1
+
+              // Append any remaining vertices in original order
+              for (int i = 3; i < face.Length; i++) {
+                outputBuilder.Append(" " + face[i]);
+              }
+            }
+            outputBuilder.AppendLine();
+          }
+        } else {
+          // Copy non-vertex lines as-is
+          outputBuilder.AppendLine(line);
+        }
+      }
+      // Write the scaled OBJ to the target file
+      File.WriteAllText(targetFilePath, outputBuilder.ToString());
+    }
+  }
+}