drawing a rectangle creat and draw function

rect.cpp

void Rect::create()
{
	static float a = 0;
	a += 0.01f;
	std::vector<float> vertex_buffer_data = {
		0.0f + a, 0.0f + a, a,
		0.3f + a, 0.0f + a, a,
		0.3f + a, 0.3f + a, a,
		0.0f + a, 0.0f + a, a,
		0.3f + a, 0.3f + a, a,
		0.0f + a, 0.3f + a, a
	};

	std::vector<float> uv_buffer_data = {
		0.0f, 1.0f,
		1.0f, 1.0f,
		1.0f, 0.0f,
		0.0f, 1.0f,
		1.0f, 0.0f,
		0.0f, 0.0f
	};

	vert_size = vertex_buffer_data.size() / 3;

	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);

	glGenBuffers(1, &vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(float) * vertex_buffer_data.size(), &vertex_buffer_data[0], GL_STATIC_DRAW);

	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);

	glGenBuffers(1, &uv_buffer);
	glBindBuffer(GL_ARRAY_BUFFER, uv_buffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(float) * uv_buffer_data.size(), &uv_buffer_data[0], GL_STATIC_DRAW);

	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);

	glBindVertexArray(0);
}


void Rect::draw() const
{
	glm::mat4 MVP = Molten::getInstance().getMVP();
	glm::mat4 model = Molten::getInstance().getModel();
	MVP = MVP * model;

	shader->useShader();

	glUniformMatrix4fv(shader->getUniformLoc("MVP"), 1, GL_FALSE, &MVP[0][0]);
	glUniform4f(shader->getUniformLoc("obj_color"), obj_color.r, obj_color.g, obj_color.b, obj_color.a);

	glBindVertexArray(vao);
	glDrawArrays(GL_TRIANGLES, 0, vert_size);
	glBindVertexArray(0);
}