anchor.diff:  
   uniform sampler3D volume_tsdf;
   uniform vec3 CameraPos;
  -uniform vec3 Dimensions;
   
   float sampleDistance = limit * 0.5f;
   const float IsoValue = 0.0f;
  
positive.code:       // approximate ray-cell intersection
        sample_pos = (sample_pos - sampleStep) - sampleStep * (prev_density / (density - prev_density));
  
        float final_density = sample(sample_pos);
        #ifdef GRAD_NORMALS
        vec3 view_normal = normalize((NormalMatrix * vec4(get_gradient(sample_pos), 0.0f)).xyz);
        #else
        vec3 view_normal = normalize((NormalMatrix * vec4(blendNormals(sample_pos), 0.0f)).xyz);
        #endif
        vec3 view_pos = (gl_ModelViewMatrix * vol_to_world * vec4(sample_pos, 1.0f)).xyz;
  
        if (g_shade_mode == 3u) {
          out_Color = vec4(blendCameras(sample_pos), 1.0f);
        }
        else {
          vec3 diffuseColor = blendColors(sample_pos);
          out_Color = vec4(shade(view_pos, view_normal, diffuseColor), 1.0f);
        }
        // apply projection matrix on z component of view-space position
        gl_FragDepth = (gl_ProjectionMatrix[2].z *view_pos.z + gl_ProjectionMatrix[3].z) / -view_pos.z * 0.5f + 0.5f;
        return;
      }
  
  
negative.code: out float gl_FragDepth;
  
  #include </shading.glsl>
  
  #include </inc_bbox_test.glsl>
  
  #define GRAD_NORMALS
  
  