void setFlareBillboard( 
  inout mat4 _MODELVIEW_MATRIX, inout mat3 _MODELVIEW_NORMAL_MATRIX, 
  mat4 _VIEW_MATRIX, mat4 _MAIN_CAM_INV_VIEW_MATRIX, mat4 _MODEL_MATRIX, 
  vec3 scale, vec2 _screenOffsetScale
)
{
  _MODELVIEW_MATRIX = _VIEW_MATRIX * mat4(
    _MAIN_CAM_INV_VIEW_MATRIX[ 0 ],
    _MAIN_CAM_INV_VIEW_MATRIX[ 1 ],
    _MAIN_CAM_INV_VIEW_MATRIX[ 2 ],
    _MODEL_MATRIX[ 3 ]
  );  

  vec3 viewPosition = _MODELVIEW_MATRIX[ 3 ].xyz;

  viewPosition.xy += viewPosition.xy * _screenOffsetScale;

  _MODELVIEW_MATRIX[ 3 ].xyz = viewPosition;

  float scaleX = length( _MODEL_MATRIX[ 0 ].xyz ) * scale.x;
  float scaleY = length( _MODEL_MATRIX[ 1 ].xyz ) * scale.y;
  float scaleZ = length( _MODEL_MATRIX[ 2 ].xyz ) * scale.z;

  _MODELVIEW_MATRIX = _MODELVIEW_MATRIX * mat4(
    vec4( scaleX, 0.0, 0.0, 0.0 ),
    vec4( 0.0, scaleY, 0.0, 0.0 ),
    vec4( 0.0, 0.0, scaleZ, 0.0 ),
    vec4( 0.0, 0.0, 0.0, 1.0 )
  );

  _MODELVIEW_NORMAL_MATRIX = mat3( _MODELVIEW_MATRIX);
}