           }  // per active object loop
 
           // clamp cumulatie sample value
-          clamp(sampleColor, vec4(0.0f, 0.0f, 0.0f, 0.0f),
-                vec4(1.0f, 1.0f, 1.0f, 1.0f));
+          sampleColor = clamp(sampleColor, vec4(0.0f), vec4(1.0f));
 
           // sample accumulation
           fragmentColor =

                              vec2(density, volumes[0].transferFunctionRow));

            // lighting
            if (squareGradientLength > 0.05f)
            {
              currentColor.xyz += calculateLighting(TFColor, startpos_eye, gradient);

            }

            // clamp color
            currentColor.xyz = clamp(currentColor.xyz, vec3(0.0f), vec3(1.0f));
            currentColor.w = TFColor.w;

            // we sum up overlapping contributions
