let make_square ~texture side =
        let half = side /. 2.0 in 
        make_quad texture
        ({vertex=(-.half,   half, 0.0); tex=(0.0,0.0); normal=(0.0, 0.0,1.0)},
         {vertex=(-.half, -.half, 0.0); tex=(0.0,1.0); normal=(0.0,0.0,1.0)},
         {vertex=(  half, -.half, 0.0); tex=(1.0,1.0); normal=(0.0,0.0,1.0)},
         {vertex=(  half,   half, 0.0); tex=(1.0,0.0); normal=(0.0,0.0,1.0)})