Proportional Mod

Moves, rotates, or scales CVs relative to their proximity to a center main CV.

This tool works well when you need to smooth the surface topology and relax the CVs. For example, if you have zip zag patterns in the CV distribution you can use the tool's Smooth option to remove it.

Note: Consider using the Transform CV tool with Transform set to Prop Mod. The tool behaves similar to Proportional mod tool but its interface is more intuitive and easily allows experimentation with falloff values.

Access this tool from the Transform tool palette:

Proportional Mod Control settings

Operations

Choose whether to move, rotate, smooth, or non-proportionally scale the CVs.

Smooth – Interpolates the amount of change based on the Falloff values for averaging the CVs in the region of effect.

When Smooth is on, you select only the primary CV and the region of effect.

Move Mode

Choose XYZ to move CVs in world space.

Choose NUV to move CVs relative to their curve or surface.

NURBS Surface Options

Falloff-U/Falloff-V

Specifies the degree of effect in the U and V parametric directions. The range for these fields is from -5.00 to 5.00.

The current Falloff value and the distance of each CV from its neighbor determines the amount by which the CVs before and after the selected ones are affected in relation to the primary CV. A Falloff value of 0 applies the transformation equally over the affected region.

If the Falloff value is positive, the effect of the transformation is decreased for CVs that are further away from the primary CV: the greater the value, the greater this damping effect. The greater the number of CVs between the primary CV and the boundary of the defined region, the less effect the transformation has on each CV. The higher the number, the less effect movement has on the surrounding CVs.
If the Falloff value is negative, the effect of the transformation is increased for CVs that are further away from the primary CV. The greater the number of CVs between the primary CV and the boundary of the defined region, the greater the effect of the transformation on each CV. Surrounding CVs move farther, because the effect is multiplied, but in the opposite direction.

Preceding#-U/Preceding#-V

Specifies the number of CVs before the primary CV that you want to include in the region definition along the U and V parametric directions.

The CVs that are affected by the operation range from 0 (the default) to N, where N is the maximum possible number of CVs in that direction for the object. Hence, to select all CVs in a direction, simply drag the slider all the way to the right.

Succeeding#-U/Succeeding#-U

Specifies the number of CVs after the primary CV that you want to include in the region definition along the U and V parametric directions.

Note: For a curve, only the U direction is used.

Revert button

Undoes all your modifications since you selected the currently active CVs.

Proportional Mod tool workflows

Transform one CV and have surrounding CVs follow it

Note: Although you can use the Proportional Mod tool for this task, we highly recommend that you use the Transform CV workflow described here: Transform one CV and have surrounding CVs follow it.

Shift-select the Proportional Mod tool.
Click the CV to use as the primary CV.
Use the option box to set the following:
- The Operation to perform on the CVs.
- The number of CVs before (Preceding U and V) and after (Preceding U and V) the primary CV that will follow along.
- The Move Mode: choose XYZ to move the CVs in world space, or NUV to move the CVs relative to the surface (in the normal, U, and V).
Use the mouse or keyboard to move, scale, rotate, or smooth the primary CV.

The affected CVs (the number of CVs before and after the primary CV as specified in the option box) follow along, with the amount of transformation relative to their distance from the primary CV.

Transform CV