From 9037820f3014bd39a1f18b79fb27cdc7fa4da179 Mon Sep 17 00:00:00 2001
From: Max Rigout <71095568+maxrigout@users.noreply.github.com>
Date: Wed, 2 Aug 2023 16:59:18 -0400
Subject: [PATCH] improved color parsing

---
 fast_obj.h | 61 +++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 42 insertions(+), 19 deletions(-)

diff --git a/fast_obj.h b/fast_obj.h
index b19dd18..f1e3695 100644
--- a/fast_obj.h
+++ b/fast_obj.h
@@ -206,6 +206,9 @@ typedef struct
     /* Final mesh */
     fastObjMesh*                mesh;
 
+    /* Position index goes to color index map */
+    unsigned int*               vertex_color_index;
+
     /* Current object/group */
     fastObjGroup                object;
     fastObjGroup                group;
@@ -652,25 +655,27 @@ const char* parse_vertex(fastObjData* data, const char* ptr)
     unsigned int ii;
     float        v;
 
-
     for (ii = 0; ii < 3; ii++)
     {
         ptr = parse_float(ptr, &v);
         array_push(data->mesh->positions, v);
     }
 
-    // extract color data
-    for (ii = 0; ii < 3; ii++)
+#ifdef FAST_OBJ_ENABLE_COLOURS
+    /* Default the vertex color to the default color index */
+    array_push(data->vertex_color_index, 0);
+    ptr = skip_whitespace(ptr);
+    if (!is_newline(*ptr))
     {
-        const char* tmp = parse_float(ptr, &v);
-        // if there's no data, we default to white
-        if (tmp == ptr)
+        /* We associate the current vertex position with the vertex color */
+        data->vertex_color_index[array_size(data->vertex_color_index) - 1] = array_size(data->mesh->colors) / 3;
+        for (ii = 0; ii < 3; ++ii)
         {
-            v = 1.0f;
+            ptr = parse_float(ptr, &v);
+            array_push(data->mesh->colors, v);
         }
-        ptr = tmp;
-        array_push(data->mesh->colors, v);
     }
+#endif
 
     return ptr;
 }
@@ -762,7 +767,11 @@ const char* parse_face(fastObjData* data, const char* ptr)
         else
             vn.n = 0;
 
-        vn.c = vn.p;
+#ifdef FAST_OBJ_ENABLE_COLOURS
+        vn.c = data->vertex_color_index[vn.p];
+#else
+        vn.c = 0;
+#endif
 
         array_push(data->mesh->indices, vn);
         count++;
@@ -1365,7 +1374,9 @@ void fast_obj_destroy(fastObjMesh* m)
     array_clean(m->positions);
     array_clean(m->texcoords);
     array_clean(m->normals);
+#ifdef FAST_OBJ_ENABLE_COLOURS
     array_clean(m->colors);
+#endif
     array_clean(m->face_vertices);
     array_clean(m->face_materials);
     array_clean(m->indices);
@@ -1420,7 +1431,9 @@ fastObjMesh* fast_obj_read_with_callbacks(const char* path, const fastObjCallbac
     m->positions      = 0;
     m->texcoords      = 0;
     m->normals        = 0;
+#ifdef FAST_OBJ_ENABLE_COLOURS
     m->colors         = 0;
+#endif
     m->face_vertices  = 0;
     m->face_materials = 0;
     m->indices        = 0;
@@ -1441,17 +1454,24 @@ fastObjMesh* fast_obj_read_with_callbacks(const char* path, const fastObjCallbac
     array_push(m->normals, 0.0f);
     array_push(m->normals, 1.0f);
 
-    array_push(m->colors, 0.0f);
-    array_push(m->colors, 0.0f);
-    array_push(m->colors, 0.0f);
+#ifdef FAST_OBJ_ENABLE_COLOURS
+    /* Default white color */
+    array_push(m->colors, 1.0f);
+    array_push(m->colors, 1.0f);
+    array_push(m->colors, 1.0f);
+#endif
 
     /* Data needed during parsing */
-    data.mesh     = m;
-    data.object   = object_default();
-    data.group    = group_default();
-    data.material = 0;
-    data.line     = 1;
-    data.base     = 0;
+    data.mesh               = m;
+    data.vertex_color_index = 0;
+    data.object             = object_default();
+    data.group              = group_default();
+    data.material           = 0;
+    data.line               = 1;
+    data.base               = 0;
+
+    /* Dummy position is assigned to the dummy color */
+    array_push(data.vertex_color_index, 0);
 
 
     /* Find base path for materials/textures */
@@ -1531,7 +1551,9 @@ fastObjMesh* fast_obj_read_with_callbacks(const char* path, const fastObjCallbac
     m->position_count = array_size(m->positions) / 3;
     m->texcoord_count = array_size(m->texcoords) / 2;
     m->normal_count   = array_size(m->normals) / 3;
+#ifdef FAST_OBJ_ENABLE_COLOURS
     m->color_count    = array_size(m->colors) / 3;
+#endif
     m->face_count     = array_size(m->face_vertices);
     m->index_count    = array_size(m->indices);
     m->material_count = array_size(m->materials);
@@ -1542,6 +1564,7 @@ fastObjMesh* fast_obj_read_with_callbacks(const char* path, const fastObjCallbac
     /* Clean up */
     memory_dealloc(buffer);
     memory_dealloc(data.base);
+    array_clean(data.vertex_color_index);
 
     callbacks->file_close(file, user_data);