anchor.diff:  
   uniform sampler3D volume_tsdf;
   uniform vec3 CameraPos;
  -uniform vec3 Dimensions;
   
   float sampleDistance = limit * 0.5f;
   const float IsoValue = 0.0f;
  
positive.code: out float gl_FragDepth;
  
  #include </shading.glsl>
  
  #define GRAD_NORMALS
  
  
negative.code:       // approximate ray-cell intersection
        sample_pos = (sample_pos - sampleStep) - sampleStep * (prev_density / (density - prev_density));
  
        submitFragment(sample_pos);
        return;
      }
  
  