// Copyright 2011 Riccardo Monica

#version 120 
#extension GL_EXT_geometry_shader4: enable

vec3 ComputeNormal(in vec3 v1,in vec3 v2,in vec3 v3)
  {
  vec3 diff1 = v2 - v1;
  vec3 diff2 = v2 - v3;
  
  vec3 crossproduct = cross(diff2,diff1);

  return normalize(crossproduct);  
  }
