UVSphere::UVSphere(float radius, const glm::ivec2& segments) :
        StaticMesh(),
        radius(radius),
        segments(segments)
    {
        std::vector<float> vertices;
        std::vector<float> normals;
        std::vector<float> uvs;
        std::vector<unsigned int> indices;
        bool odd = false;
        float inv_len = 1.0f / radius;

        for (int y = 0; y <= segments.y; ++y)
        {
            for (int x = 0; x <= segments.x; ++x)
            {
                float seg_x = (float)x / (float)segments.x;
                float seg_y = (float)y / (float)segments.y;
                float theta = seg_x * 2.0f * PI;
                float phi = seg_y * PI;
                float pos_x = std::cos(theta) * std::sin(phi) * radius;
                float pos_y = std::sin(-PI / 2 + PI * seg_y) * radius;
                float pos_z = std::sin(theta) * std::sin(phi) * radius;

                vertices.push_back(pos_x);
                vertices.push_back(pos_y);
                vertices.push_back(pos_z);

                normals.push_back(pos_x);
                normals.push_back(pos_y);
                normals.push_back(pos_z);

                uvs.push_back(seg_x);
                uvs.push_back(seg_y);
            }
        }

        for (int y = 0; y < segments.y; ++y)
        {
            if (!odd)
            {
                for (int x = 0; x <= segments.x; ++x)
                {
                    indices.push_back(y       * (segments.x + 1) + x);
                    indices.push_back((y + 1) * (segments.x + 1) + x);
                }
            }
            else
            {
                for (int x = segments.x; x >= 0; --x)
                {
                    indices.push_back((y + 1) * (segments.x + 1) + x);
                    indices.push_back(y       * (segments.x + 1) + x);
                }
            }

            odd = !odd;
        }

        this->setVertices(vertices);
        this->setNormals(normals);
        this->setUvs(uvs);
        this->setIndices(indices);
        this->setDrawMode(StaticMesh::DrawMode::TRIANGLE_STRIP);
        calculateTangents();

        vao = new VertexArray();

        vbo = new VertexBuffer(getVertices().data(), (unsigned int)getVertices().size() * sizeof(float));
        vao->addBuffer(*vbo, 0, 3);

        nbo = new VertexBuffer(getNormals().data(), (unsigned int)getNormals().size() * sizeof(float));
        vao->addBuffer(*nbo, 1, 3);

        uvbo = new VertexBuffer(getUvs().data(), (unsigned int)getUvs().size() * sizeof(float));
        vao->addBuffer(*uvbo, 2, 2);

        tbo = new VertexBuffer(getTangents().data(), (unsigned int)getTangents().size() * sizeof(float));
        vao->addBuffer(*tbo, 3, 3);

        ibo = new IndexBuffer(getIndices().data(), (unsigned int)getIndices().size());

        setVertexCount((unsigned int)getVertices().size() / 3);
        setName("SphereStaticMesh");
    }