  uniform float scale;
  uniform float screenWidth;
  uniform float screenHeight;

    void main() 
    {
      float x = 1.0*scale/screenWidth;
      float y = 1.0*scale/screenHeight;

      vec2 dg1 = vec2( x, y);
      vec2 dg2 = vec2(-x, y);
      vec2 dx = vec2(x, 0.0);
      vec2 dy = vec2(0.0, y);

      gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
      gl_TexCoord[0] = gl_MultiTexCoord0;
      gl_TexCoord[1].xy = gl_TexCoord[0].xy - dg1;
      gl_TexCoord[1].zw = gl_TexCoord[0].xy - dy;
      gl_TexCoord[2].xy = gl_TexCoord[0].xy - dg2;
      gl_TexCoord[2].zw = gl_TexCoord[0].xy + dx;
      gl_TexCoord[3].xy = gl_TexCoord[0].xy + dg1;
      gl_TexCoord[3].zw = gl_TexCoord[0].xy + dy;
      gl_TexCoord[4].xy = gl_TexCoord[0].xy + dg2;
      gl_TexCoord[4].zw = gl_TexCoord[0].xy - dx;
    }