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Add OBJ mesh support to Unity plugin

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Balint-H
2025-01-21 15:11:27 +00:00
parent 36cbef50b7
commit a58f8d0033
4 changed files with 96 additions and 76 deletions
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unity/Editor/Importer/ObjMeshImportUtility.cs
+66 -65
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@@ -11,84 +11,85 @@
// 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 UnityEditor;
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);
/// <summary>
/// Scale vertex data manually line by line. We skip normals. Warning: Parameter vertex points
/// (`vp`) were unclear to me how to handle with scaling, 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;
public static void CopyAndScaleOBJFile(string sourceFilePath, string targetFilePath,
Vector3 scale) {
// 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. It is unclear to me why flipping along x axis was necessary,
// but without it meshes were incorrectly oriented.
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;
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);
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 ")) {
// We swizzle the normals too
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 ") && scale.x*scale.y*scale.z < 0) {
// Faces definition, flip face by reordering vertices
string[] parts = line.Split(' ');
if (parts.Length >= 4) {
outputBuilder.Append(parts[0]+" ");
var face = parts.Skip(1).ToArray();
if (face.Length >= 3) {
outputBuilder.Append(face[0]+" ");
outputBuilder.Append(face[2]+" ");
outputBuilder.Append(face[1]);
}
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());
}
// Write the scaled OBJ to the target file
File.WriteAllText(targetFilePath, outputBuilder.ToString());
}
}
}