 uniform sampler3D volumeSampler;
 
 const float DEPTH_NOT_SET = -10.0f;
+const float EARLY_RAY_TERMINATION_ALPHA = 0.999f;
 
 #define transferFunctionRowCount 64.0f
 

    }

    // early ray termination
    if (fragmentColor.a > 0.999)
      break;

    currentPos_eye += step_eye;

      accumulatedOutputColor = blend(accumulatedOutputColor, currentFragment.color);
    }

    if (finalColor.a > EARLY_RAY_TERMINATION_ALPHA)
      break;

    // break; // just the first fragment
