The Twist SOP performs non-linear deformations such as bend, linear taper, shear, squash and stretch, taper and twist. Each deformation will distort the object in one or more axes.
All deformations occur around the Primary Axis. If the Primary Axis is Y, then the Y value does not get changed. For deformations that use the Secondary Axis, the points along the Secondary Axis will not be changed. Edges that are parallel to the Primary Axis will remain parallel during the transformation.
/group - If there are input groups, specifying a group name in this field will cause this SOP to act only upon the group specified. Accepts patterns, as described in Pattern Matching.
/op - This menu allows you to select a type of non-linear deformation. Select from the following options:
- Twist - Rotates the input geometry around the Primary Axis.
- Bend - Bends the input geometry about the Primary Axis while keeping points on the Secondary Axis stationary.
- Shear - Shears the input geometry along the Secondary Axis while looking down the Primary Axis.
- Taper - Tapers the input geometry along the Secondary Axis while looking down the Primary Axis.
- Linear Taper - Tapers the input geometry as with the Taper option; however, only the edges remain straight through the Taper operation.
- Squash and Stretch - Traditional animator's bounce tools.
Primary Axis / Secondary Axis
/paxis /saxis - These menus allows you to select the primary and secondary axes for the deformation. The selected deformation will first occur in the Primary Axis and then the Secondary Axis.
/px /py /pz - This field allows you to choose the origin of the deformation.
Strength / Roll Off
/strength /roll - The Strength of the effect being applied. The Rolloff determines an accentuation of the effect being applied. When you are using different types of transformations this Strength / Roll will have different effects:
- Bend - Strength and Roll are used to control the extremities of the geometry (try a value of 0.5).
- Twist - Strength and Roll are used to affect the twist amount based on the distance.
- Shear - Strength and Roll are used to affect the shear amount based on distance.
- Taper - Strength and Roll are used to affect the direction of the bow (inwards vs. outwards).
- Linear Taper - Strength and Roll have no effect for this option.
- Squash and Stretch - Strength and Roll are used to maintain the apparent volume of the source geometry.
Typically, Rolloff should equal
1 - which spreads the effect evenly (although not being limited to) across the bounds of the geometry. Values higher than
1 iterate the effect multiple times through the same range. If Rolloff equals
0, then the effect may be localised to a small segment at the centre of the deformed geometry and Strength may not appear to work properly.
Note: To be certain to see the effects of the Twist SOP, make sure you have enough divisions along the edges. By using a centre that is different from that of the object you can improve your control of the object. Try moving the pivot point to the bottom of an object that you are squashing and stretching.
Inputs / Geometry Types
Input 1 - Twist Source - Can be any geometry, including NURBS and Bziers), but should have sufficient points for a better deformation. Use the Divide or Refine SOPs to achieve this.
Uses / Works in Relation With
Generalized non-linear deformations such as bend, linear taper, shear, squash and stretch, taper and twist.
$CEZ- Defines the centroid of the input geometry.
$ZMAX- Defines the extent of the bounding box for the input geometry.
$SIZEZ- The size of the bounding box of the input geometry.