csg_group(object_list)

#Group four spheres together and merge them with a box:
generate_ground(material=diffuse(checkercolor="grey20")) %>% 
  add_object(csg_object(csg_combine(
  csg_group(list(csg_sphere(x=1,z=1, radius=0.5),csg_sphere(x=-1,z=1, radius=0.5),
                 csg_sphere(x=1,z=-1, radius=0.5),csg_sphere(x=-1,z=-1, radius=0.5))),
  csg_box(y=0.5, width=c(2,0.2,2)), operation="blend"), material=glossy(color="red"))) %>%
  add_object(sphere(y=10,x=-5,radius=3,material=light(intensity=10))) %>% 
  render_scene(clamp_value=10,lookfrom=c(5,5,10))