MCG offers several ways to create and manipulate splines. The Splines category contains many nodes and compounds that you can use in your graphs.
Getting Data from Splines in the Scene
Use SplineFromNode in your graph to allow a tool's users to specify a spline object in the scene. It's a good practice to use CanGetSplineFromNode with an If node to check the specified scene object, and take an appropriate action if no valid spline has been specified.
After that, you can use other nodes in the Splines category, such as SplineVerticesBuffer or SplineTangentsBuffer, to get data from the spline and then perform operations on the resulting arrays.
Creating Spline Data
- CreateSplineFromKnots creates a linear spline from an array of positions.
- CreateSplineFromBuffers has additional options for tangents and segment types.
Many of the compounds in the Splines category provide examples of using these nodes to create splines from scratch, or based on data in the scene.
Creating Spline Shapes
There are a couple of ways to create spline shapes in a scene.
- One way is to create a graph that terminates in an
Output: shape node. When compiled, the tool appears on the
Create panel, when you select the
Shapes category and then select the
Max Creation Graph sub-category.
When using Output: shape, you can use the implicit parameter node Shape: Matrix to get the world space transformation matrix.
- Alternatively, you can use a CreateEditableSpline node in the graph of any tool. Typically, you should use an If node connected to a Param: Signal node so that the tool does not create a new spline shape every time it evaluates, but only when users click a button in its rollout. You can open the graph of the CFDSplineNode tool to see an example of this technique.
Modifying Splines
You cannot create modifiers that can be applied to a spline shape. However, you can use SplineToMesh to store spline data as a mesh, to which modifiers can be applied. You can either leave the data as a mesh for further modification, or convert it back using MeshToSpline and create a spline shape in the scene.