From 4e564326d0a302e27bf773eee9b1bdb88dfda884 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Wed, 15 Jan 2025 19:45:08 +0100
Subject: fix(engine): make Mesh indices produced by Obj::to_mesh useful

---
 engine/src/file_format/wavefront/obj.rs | 49 +++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 21 deletions(-)

(limited to 'engine/src/file_format')

diff --git a/engine/src/file_format/wavefront/obj.rs b/engine/src/file_format/wavefront/obj.rs
index 88e6580..6ca11c2 100644
--- a/engine/src/file_format/wavefront/obj.rs
+++ b/engine/src/file_format/wavefront/obj.rs
@@ -2,6 +2,7 @@
 //!
 //! File format documentation: <https://paulbourke.net/dataformats/obj>
 
+use std::collections::HashMap;
 use std::fs::read_to_string;
 use std::path::PathBuf;
 
@@ -82,26 +83,32 @@ impl Obj
     /// - A face index does not fit in a [`u32`]
     pub fn to_mesh(&self) -> Result<Mesh, Error>
     {
-        let vertices = self
-            .faces
-            .iter()
-            .flat_map(|face| face.vertices.clone())
-            .map(|face_vertex| face_vertex.to_vertex(self))
-            .collect::<Result<Vec<_>, Error>>()?;
-
-        Ok(Mesh::new(
-            vertices,
-            Some(
-                self.faces
-                    .iter()
-                    .flat_map(|face| face.vertices.clone())
-                    .enumerate()
-                    .map(|(index, _)| {
-                        u32::try_from(index).map_err(|_| Error::FaceIndexTooBig(index))
-                    })
-                    .collect::<Result<Vec<_>, _>>()?,
-            ),
-        ))
+        let mut vertices = Vec::<Vertex>::with_capacity(self.faces.len() * 3);
+        let mut indices = Vec::<u32>::with_capacity(self.faces.len() * 3);
+
+        let mut added_face_vertices =
+            HashMap::<FaceVertex, u32>::with_capacity(self.faces.len() * 3);
+
+        for face in &self.faces {
+            for face_vertex in &face.vertices {
+                if let Some(index) = added_face_vertices.get(&face_vertex) {
+                    indices.push(*index);
+
+                    continue;
+                }
+
+                vertices.push(face_vertex.to_vertex(self)?);
+
+                let vertex_index = u32::try_from(vertices.len() - 1)
+                    .map_err(|_| Error::FaceIndexTooBig(vertices.len() - 1))?;
+
+                indices.push(vertex_index);
+
+                added_face_vertices.insert(face_vertex.clone(), vertex_index);
+            }
+        }
+
+        Ok(Mesh::new(vertices, Some(indices)))
     }
 
     /// Reads and parses the material libraries of this `Obj`.
@@ -142,7 +149,7 @@ pub struct Face
     pub material_name: Option<String>,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct FaceVertex
 {
     pub position: u32,
-- 
cgit v1.2.3-18-g5258