By Lisa Swinnard

Continued from part 1.

Adjusting the value clipping has an effect on the volume of the intrusion, as well as its continuity. The volume of the intrusion can be determined by right clicking the Output Volume > Properties, and the continuity of an intrusion is represented by the number of parts it comprises (fewer parts = greater continuity). Below is a series of examples that show how value clipping affects the volume and continuity of this intrusion.

Automatic Clipping (Lower and Upper Bound Equal +/- 21.66)

No Clipping (Lower Bound -312, Upper Bound +209)

Equal Weighting of Positive and Negative Values (Clipped to the Max/Min Values)

Manual Clipping (Limits – Lower Bound -1.3, Upper Bound +1.3)

Higher Weighting to Positive Values

Manual Clipping (Limits – Lower Bound -1.3, Upper Bound +2.3)

Manual Clipping (Limits – Lower Bound -1.3, Upper Bound +5.3)

Manual Clipping (Limits – Lower Bound -1.3, Upper Bound +10.3)

Manual Clipping (Lower Bound -100, Upper Bound +209)

Higher Weighting to Negative Values

Manual Clipping (Lower Bound -2.3, Upper Bound +1.3)

Manual Clipping (Lower Bound -5.3, Upper Bound +1.3)

Manual Clipping (Lower Bound -10.3, Upper Bound +1.3)

Manual Clipping (Lower Bound -209, Upper Bound +100)

## Comparisons and Observations:

• Figures A and B – the automatic clipping provides greater continuity to the intrusion (4 vs. 5 parts), as well as a slightly reduced volume (reduced relative influence of negative values).
• Figure C – reducing the clipped value to the lowest possible value results in an increase in continuity.
• Figures D, E, F – using Figure C as a baseline, Figures D, E and F show that increasing the weight of the positive values, while clipping the negative value to its upper limit, increase both the volume and continuity of the intrusion. The influence of the positive values (i.e. the values within the intrusion) is greater than the influence of the negative values, allowing the surface to expand. Figure F is an extreme example.
• Figure G – the relative difference (ratio) between the negative and positive values has a greater effect on the intrusion volume and continuity than the absolute difference.
• Figures H, I, J – using Figure C as a baseline, Figures H, I and J show that increasing the weight of the negative values, while clipping the positive value to its lower limit, decrease both the volume and continuity of the intrusion. The influence of the negative values (i.e. the values outside of the intrusion) is greater than the influence of the positive values, forcing the surface to contract. Figure J is an extreme example.
• Figure K – the relative difference (ratio) between the negative and positive values has a greater effect on the intrusion volume and continuity than the absolute difference.
• Modifying the surface distance offset and background fill spacing in the point generation window will also have a small effect on the overall volume and continuity.

In summary, value clipping, while often overlooked during surface editing, can have significant effect on the overall size and shape of an intrusion surface.