#macro front_wall_small_gate( tag, g_dim, g_dx, g_open )

  // The small (pedestrian) gate.
  
  // {tag}    tag for part identification.
  // {g_dim}  dimensions of gate.
  // {g_dx}   X coordinate of back face of gate.
  // {g_open} If 1, show gate half-open.
  
  #local g_frame_sy = 40; // Y width of frame.

  // The wing (mobile part) of the gate:
  #local g_wing_tag = concat( tag, ".w1" )
  #local g_wing_dim = g_dim - 2*g_frame_sy*y;
  #local g_grille = object{ front_wall_grille( g_wing_tag, g_wing_dim ) texture { tx_grille } }
  #local g_wing = object{ g_grille }
  
  // The fixed part of the gate:
  #local g_frame = sphere{ g_dim/2, 20 texture{ tx_bug } } // !!! Define !!!
  
  // Opening angle:
  #local g_open_deg = 60*g_open;
  
  #local gate = 
    union{
      object{ g_frame }
      object{ g_wing 
        translate - g_wing_dim.x*x
        rotate g_open_deg*z 
        translate + g_wing_dim.x*x + g_frame_sy*y
      }
    }

  gate 
  
#end