   if (maxAge == 0)
     discard;  // no fragment, early exit
 
+  vec4 farPlane = vec4(0, 0, 1, depthCutOff);
+
   int activeObjects = 0;
   FragmentData currentFragment;
   FragmentData nextFragment;

      ++age;
  }

  for (--age; age < maxAge; age++)  // all fragments
  {
    currentFragment = nextFragment;

uniform vec3 textureAtlasSize;
uniform vec3 sampleDistance;
uniform float alphaThresholdForDepth = 0.1;
uniform float depthCutOff = 0.0;

uniform sampler3D volumeSampler;

