From 69175c08f04fda3af4b7e9b969dd20ce8d280792 Mon Sep 17 00:00:00 2001
From: Elias Stepanik <40958815+eliasstepanik@users.noreply.github.com>
Date: Wed, 18 Jun 2025 20:36:17 +0200
Subject: [PATCH] Add OBJ voxelization helper

---
 client/Cargo.toml                             |  3 ++
 .../environment/systems/voxels/octree.rs      | 47 ++++++++++++++++++-
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/client/Cargo.toml b/client/Cargo.toml
index a373ba7..662f3a9 100644
--- a/client/Cargo.toml
+++ b/client/Cargo.toml
@@ -23,4 +23,7 @@ rayon = "1.10.0"
 bincode = "1.3"
 bevy_app_compute = "0.16"
 bytemuck = { version = "1.14", features = ["derive"] }
+obj = "0.10"
+voxelize-rs = "0.1"
+nalgebra = "0.18"
 
diff --git a/client/src/plugins/environment/systems/voxels/octree.rs b/client/src/plugins/environment/systems/voxels/octree.rs
index bbaf41d..a010295 100644
--- a/client/src/plugins/environment/systems/voxels/octree.rs
+++ b/client/src/plugins/environment/systems/voxels/octree.rs
@@ -1,6 +1,6 @@
 use crate::plugins::environment::systems::voxels::structure::{
-    ChunkKey, DirtyVoxel, OctreeNode, Ray, SparseVoxelOctree, Voxel, AABB, CHUNK_SIZE,
-    NEIGHBOR_OFFSETS,
+    AABB, CHUNK_SIZE, ChunkKey, DirtyVoxel, NEIGHBOR_OFFSETS, OctreeNode, Ray, SparseVoxelOctree,
+    Voxel,
 };
 use bevy::asset::Assets;
 use bevy::math::{DQuat, DVec3};
@@ -589,4 +589,47 @@ impl SparseVoxelOctree {
             self.occupied_chunks.insert(key);
         }
     }
+
+    /// Load a Wavefront `.obj` file and insert all triangles as voxels.
+    /// `voxel_size` defines the world-space size of the generated voxels.
+    pub fn insert_obj_file<P: AsRef<Path>>(
+        &mut self,
+        path: P,
+        voxel: Voxel,
+        voxel_size: f32,
+    ) -> Result<(), Box<dyn std::error::Error>> {
+        use obj::Obj;
+        use voxelize_rs::{Triangle, Vector3, voxelize};
+
+        let obj: Obj<obj::TexturedVertex> = Obj::load(path)?;
+
+        let mut tris = Vec::new();
+        for object in &obj.data.objects {
+            for group in &object.groups {
+                for poly in &group.polys {
+                    if poly.0.len() < 3 {
+                        continue;
+                    }
+                    for i in 1..poly.0.len() - 1 {
+                        let v0 = obj.data.position[poly.0[0].0];
+                        let v1 = obj.data.position[poly.0[i].0];
+                        let v2 = obj.data.position[poly.0[i + 1].0];
+                        tris.push(Triangle::new(
+                            Vector3::new(v0[0], v0[1], v0[2]),
+                            Vector3::new(v1[0], v1[1], v1[2]),
+                            Vector3::new(v2[0], v2[1], v2[2]),
+                        ));
+                    }
+                }
+            }
+        }
+
+        let size = Vector3::new(voxel_size, voxel_size, voxel_size);
+        let voxels = voxelize(&tris, &size);
+        for p in voxels {
+            self.insert(Vec3::new(p.x, p.y, p.z), voxel);
+        }
+
+        Ok(())
+    }
 }