When the Spline IK Control modifier is applied to a spline, you can select and transform its vertices without having to access the vertex sub-object level.
The Spline IK Control Modifier can also place helpers at each vertex location to aid in moving vertices.
The Spline IK Control modifier works by placing knots (control points) at each vertex. The knots can then be used to control vertices, which in turn reshape the spline.
This modifier also works on NURBS curves, placing a knot at each control point or control vertex (CV).
Use the Spline IK Control modifier to prepare a spline or NURBS curve for use with the Spline IK Solver.
When helpers are created, knot numbers and their corresponding names appear here. Knot #1 is placed at the first vertex on the spline, and additional knots are numbered in sequence.
Places a helper at each knot, and displays knot numbers and helper names in the Control Objects area. Helper display is based on selections in the Helper Display group. Helpers are linked upon creation if a linking option is selected in the Link Types group.
These options cause helpers to be linked upon creation.
When you click Create Helpers, 3ds Max can place one or more Point helper objects at each knot, making it easier to move and animate the knots. You can enable more than one type of helper.
Places a small X-shaped Point helper at each knot.
Places a small tripod-axis-shaped Point helper at each knot.
Places a small cross-shaped Point helper at each knot.
Places a small box-shaped Point helper at each knot.
Sets the size for helpers.
Keeps the sizes of helpers constant regardless of the zoom extent of the viewports.
Displays the helpers on top of all other objects in the scene for improved visibility in busy scenes.