3DFileViewer: Move Demos/GLTeapot to Applications/3DFileViewer

Also changes the category to `Graphics`

Userland/Applications/3DFileViewer/WavefrontOBJLoader.cpp

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ * Copyright (c) 2021, Mathieu Gaillard <gaillard.mathieu.39@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "WavefrontOBJLoader.h"
+#include <LibCore/File.h>
+#include <stdlib.h>
+
+RefPtr<Mesh> WavefrontOBJLoader::load(const String& fname)
+{
+    auto obj_file_or_error = Core::File::open(fname, Core::OpenMode::ReadOnly);
+    Vector<Vertex> vertices;
+    Vector<Triangle> triangles;
+
+    dbgln("Wavefront: Loading {}...", fname);
+
+    if (obj_file_or_error.is_error())
+        return nullptr;
+
+    // Start reading file line by line
+    for (auto line = obj_file_or_error.value()->line_begin(); !line.at_end(); ++line) {
+        auto object_line = *line;
+
+        // FIXME: Parse texture coordinates and vertex normals
+        if (object_line.starts_with("vt") || object_line.starts_with("vn")) {
+            continue;
+        }
+
+        // This line describes a vertex (a position in 3D space)
+        if (object_line.starts_with("v")) {
+            auto vertex_line = object_line.split_view(' ');
+            if (vertex_line.size() != 4) {
+                dbgln("Wavefront: Malformed vertex line. Aborting.");
+                return nullptr;
+            }
+
+            vertices.append(
+                { static_cast<GLfloat>(atof(String(vertex_line.at(1)).characters())),
+                    static_cast<GLfloat>(atof(String(vertex_line.at(2)).characters())),
+                    static_cast<GLfloat>(atof(String(vertex_line.at(3)).characters())) });
+        }
+        // This line describes a face (a collection of 3 vertices, aka a triangle)
+        else if (object_line.starts_with("f")) {
+            auto face_line = object_line.split_view(' ');
+            if (face_line.size() != 4) {
+                dbgln("Wavefront: Malformed face line. Aborting.");
+                return nullptr;
+            }
+
+            if (object_line.contains("/")) {
+                for (int i = 1; i <= 3; ++i) {
+                    face_line.at(i) = face_line.at(i).split_view("/").at(0);
+                }
+            }
+
+            // Create a new triangle
+            triangles.append(
+                {
+                    face_line.at(1).to_uint().value() - 1,
+                    face_line.at(2).to_uint().value() - 1,
+                    face_line.at(3).to_uint().value() - 1,
+                });
+        }
+    }
+
+    if (vertices.is_empty()) {
+        dbgln("Wavefront: Failed to read any data from 3D file: {}", fname);
+        return nullptr;
+    }
+
+    dbgln("Wavefront: Done.");
+    return adopt_ref(*new Mesh(vertices, triangles));
+}