Applications: Support `.obj` polygons in `3DFileViewer`

Our `WavefrontOBJLoader` only supported faces with 3 vertices, but
`.obj` files can specify arbitrary polygons with 4 or more vertices.

1 files changed, 32 insertions, 41 deletions

diff --git a/Userland/Applications/3DFileViewer/WavefrontOBJLoader.cpp b/Userland/Applications/3DFileViewer/WavefrontOBJLoader.cpp
index ae239544e5..2ccecbb575 100644
--- a/Userland/Applications/3DFileViewer/WavefrontOBJLoader.cpp
+++ b/Userland/Applications/3DFileViewer/WavefrontOBJLoader.cpp
@@ -7,9 +7,15 @@
  */
 
 #include "WavefrontOBJLoader.h"
+#include <AK/FixedArray.h>
 #include <LibCore/File.h>
 #include <stdlib.h>
 
+static inline GLuint get_index_value(StringView& representation)
+{
+    return representation.to_uint().value_or(1) - 1;
+}
+
 RefPtr<Mesh> WavefrontOBJLoader::load(Core::File& file)
 {
     Vector<Vertex> vertices;
@@ -29,7 +35,6 @@ RefPtr<Mesh> WavefrontOBJLoader::load(Core::File& file)
             auto tex_coord_line = object_line.split_view(' ');
             if (tex_coord_line.size() != 3) {
                 dbgln("Wavefront: Malformed TexCoord line. Aborting.");
-                dbgln("{}", object_line);
                 return nullptr;
             }
 
@@ -68,54 +73,40 @@ RefPtr<Mesh> WavefrontOBJLoader::load(Core::File& file)
             continue;
         }
 
-        // This line describes a face (a collection of 3 vertices, aka a triangle)
+        // This line describes a face (a collection of 3+ vertices, aka a triangle or polygon)
         if (object_line.starts_with("f")) {
-            auto face_line = object_line.split_view(' ');
-            if (face_line.size() != 4) {
+            auto face_line = object_line.substring_view(2).split_view(' ');
+            auto number_of_vertices = face_line.size();
+            if (number_of_vertices < 3) {
                 dbgln("Wavefront: Malformed face line. Aborting.");
                 return nullptr;
             }
 
-            GLuint vert_index[3];
-            GLuint tex_coord_index[3];
-            GLuint normal_index[3];
-            if (object_line.contains("/")) {
-                for (int i = 1; i <= 3; ++i) {
-                    auto vertex_data = face_line.at(i).split_view("/", true);
-
-                    vert_index[i - 1] = vertex_data.at(0).to_uint().value_or(1);
-                    tex_coord_index[i - 1] = vertex_data.at(1).to_uint().value_or(1);
-
-                    if (vertex_data.size() == 3)
-                        normal_index[i - 1] = vertex_data.at(2).to_uint().value_or(1);
-                    else
-                        normal_index[i - 1] = 1;
-                }
-            } else {
-                vert_index[0] = (face_line.at(1).to_uint().value_or(1));
-                vert_index[1] = (face_line.at(2).to_uint().value_or(1));
-                vert_index[2] = (face_line.at(3).to_uint().value_or(1));
-                tex_coord_index[0] = 0;
-                tex_coord_index[1] = 0;
-                tex_coord_index[2] = 0;
-                normal_index[0] = 0;
-                normal_index[1] = 0;
-                normal_index[2] = 0;
+            auto vertex_indices = FixedArray<GLuint>::must_create_but_fixme_should_propagate_errors(number_of_vertices);
+            auto tex_coord_indices = FixedArray<GLuint>::must_create_but_fixme_should_propagate_errors(number_of_vertices);
+            auto normal_indices = FixedArray<GLuint>::must_create_but_fixme_should_propagate_errors(number_of_vertices);
+
+            for (size_t i = 0; i < number_of_vertices; ++i) {
+                auto vertex_parts = face_line.at(i).split_view('/', true);
+                vertex_indices[i] = get_index_value(vertex_parts[0]);
+                tex_coord_indices[i] = (vertex_parts.size() >= 2) ? get_index_value(vertex_parts[1]) : 0;
+                normal_indices[i] = (vertex_parts.size() >= 3) ? get_index_value(vertex_parts[2]) : 0;
             }
 
-            // Create a new triangle
-            triangles.append(
-                {
-                    vert_index[0] - 1,
-                    vert_index[1] - 1,
-                    vert_index[2] - 1,
-                    tex_coord_index[0] - 1,
-                    tex_coord_index[1] - 1,
-                    tex_coord_index[2] - 1,
-                    normal_index[0] - 1,
-                    normal_index[1] - 1,
-                    normal_index[2] - 1,
+            // Create a triangle for each part of the polygon
+            for (size_t i = 0; i < number_of_vertices - 2; ++i) {
+                triangles.append({
+                    vertex_indices[0],
+                    vertex_indices[i + 1],
+                    vertex_indices[i + 2],
+                    tex_coord_indices[0],
+                    tex_coord_indices[i + 1],
+                    tex_coord_indices[i + 2],
+                    normal_indices[0],
+                    normal_indices[i + 1],
+                    normal_indices[i + 2],
                 });
+            }
         }
     }