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

Also changes the category to `Graphics`

Userland/Applications/3DFileViewer/Mesh.cpp

@@ -0,0 +1,91 @@
+/*
+ * 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 <LibGL/GL/gl.h>
+#include <LibGfx/Color.h>
+#include <LibGfx/Vector3.h>
+#include <LibGfx/Vector4.h>
+
+#include "Mesh.h"
+
+const Color colors[] {
+    Color::Red,
+    Color::Green,
+    Color::Blue,
+    Color::Magenta,
+    Color::Yellow,
+    Color::Cyan,
+    Color::White
+};
+
+Mesh::Mesh(Vector<Vertex> vertices, Vector<Triangle> triangles)
+    : m_vertex_list(move(vertices))
+    , m_triangle_list(move(triangles))
+{
+}
+
+void Mesh::draw()
+{
+    // Light direction
+    const FloatVector3 light_direction(1.f, 1.f, 1.f);
+
+    // Mesh color
+    const FloatVector4 mesh_ambient_color(0.2f, 0.2f, 0.2f, 1.f);
+    const FloatVector4 mesh_diffuse_color(0.6f, 0.6f, 0.6f, 1.f);
+
+    for (u32 i = 0; i < m_triangle_list.size(); i++) {
+        const auto& triangle = m_triangle_list[i];
+
+        const FloatVector3 vertex_a(
+            m_vertex_list.at(triangle.a).x,
+            m_vertex_list.at(triangle.a).y,
+            m_vertex_list.at(triangle.a).z);
+
+        const FloatVector3 vertex_b(
+            m_vertex_list.at(triangle.b).x,
+            m_vertex_list.at(triangle.b).y,
+            m_vertex_list.at(triangle.b).z);
+
+        const FloatVector3 vertex_c(
+            m_vertex_list.at(triangle.c).x,
+            m_vertex_list.at(triangle.c).y,
+            m_vertex_list.at(triangle.c).z);
+
+        // Compute the triangle normal
+        const FloatVector3 vec_ab = vertex_b - vertex_a;
+        const FloatVector3 vec_ac = vertex_c - vertex_a;
+        const FloatVector3 normal = vec_ab.cross(vec_ac).normalized();
+
+        // Compute lighting with a Lambertian color model
+        const auto light_intensity = max(light_direction.dot(normal), 0.f);
+        const FloatVector4 color = mesh_ambient_color
+            + mesh_diffuse_color * light_intensity;
+
+        glBegin(GL_TRIANGLES);
+        glColor4f(color.x(), color.y(), color.z(), color.w());
+
+        // Vertex 1
+        glVertex3f(
+            m_vertex_list.at(m_triangle_list[i].a).x,
+            m_vertex_list.at(m_triangle_list[i].a).y,
+            m_vertex_list.at(m_triangle_list[i].a).z);
+
+        // Vertex 2
+        glVertex3f(
+            m_vertex_list.at(m_triangle_list[i].b).x,
+            m_vertex_list.at(m_triangle_list[i].b).y,
+            m_vertex_list.at(m_triangle_list[i].b).z);
+
+        // Vertex 3
+        glVertex3f(
+            m_vertex_list.at(m_triangle_list[i].c).x,
+            m_vertex_list.at(m_triangle_list[i].c).y,
+            m_vertex_list.at(m_triangle_list[i].c).z);
+
+        glEnd();
+    }
+}