def billboard_matrix():
 m = get_model_matrix()
 m[0] = 1
 m[1] = 0
 m[2] = 0
 m[4] = 0
 m[5] = 1
 m[6] = 0
 m[8] = 0
 m[9] = 0
 m[10] = 1
 glLoadMatrixf(m)

def billboard_matrix ( ) : m = get_model_matrix ( ) m [ 0 ] = 1 m [ 1 ] = 0 m [ 2 ] = 0 m [ 4 ] = 0 m [ 5 ] = 1 m [ 6 ] = 0 m [ 8 ] = 0 m [ 9 ] = 0 m [ 10 ] = 1 glLoadMatrixf ( m )
removes rotational components of current matrix so that primitives are always drawn facing the viewer .