In brief
- SubDLoft creates a SubD object from selected curves.
- For closed curves, you can adjust the position and direction of edge loop points.
- Curves suited to SubD with matching control point counts can produce a simpler result.
- Join connects a SubD edge to a loft, but does not support History recording.
The SubDLoft command, described in McNeel’s Rhino 8 help documentation, creates a SubD object from selected curves that define a shape. This guide covers the command’s curve preparation, edge loop editing, and segment control options in Rhino 8, within a workflow for architecture, interior design, and visualization. Since the documentation does not specify a fixed setting that applies to every project, choices should be evaluated based on the model’s geometry.
You can access the command via SubD Sidebar › SubD › Loft. You can also select curve segments as a chain or use only part of a curve. The steps below help you systematically review input curves and command options before creating the model.
How do you prepare curves for SubDLoft?
Determine the order of the sections. SubDLoft creates a shape using the selected curves. Treat the curves as sections of the intended form and check their arrangement in the model before running the command. The documentation does not prescribe a single selection order for all projects; proceed according to the shape you intend to create.
Compare control point counts. According to McNeel, if curves are suited to SubD and have the same number of control points, they can produce a simpler SubD. Different control point counts may complicate the structure; in that case, it is also not guaranteed that the resulting SubD will pass through every input curve. Checking the curve structure can help reduce discrepancies between the expected and resulting shapes.
Check whether the curves are open or closed. This distinction affects the availability of some options. For example, options for managing edge loop point positions are for closed curves. For open curves, the Corners option is available for the end points.
Select part of the input geometry if needed. SubCrv lets you use a specific section of a curve instead of the entire curve as input. Chain selects connected curve or edge segments as a single curve input. However, Chain does not create a simple SubD from SubD edge chains; clicking, window selection, or double-clicking can be used for that purpose.
How do you adjust edge loops on closed curves?
The positions of edge loop points on closed curves are important in determining how the loft relates the sections. Rhino 8’s Flip, Automatic, and Natural options provide different ways to control the direction or placement of these points. Flip reverses the curve direction; Automatic attempts to arrange loop points and directions so they match. Natural moves the points back to their positions when the command was started.
When you need to adjust points manually, select each one and move it along its curve to align it with the other loop points. If the direction indicators need to face the same way, consider using Flip. SnapToKnots determines whether points are constrained to knot locations: when set to Yes, movement is limited to knots; No allows the points to move without this constraint.
| Setting | When to use it | Effect |
|---|---|---|
| Flip | When the curve direction needs to be reversed | Reverses the curve direction. |
| Automatic | When automatic arrangement of points and directions is desired | Applies automatic alignment to match edge loops. |
| Natural | When you need to return to the initial point arrangement | Moves the points to where they were when the command started. |
| SnapToKnots | When setting the limits on point movement | Yes constrains movement to knot points; No allows free movement. |
The table does not recommend a “best” value for a specific project; the source documentation does not define one. Testing the options on a small sample geometry can help you find the right control method, especially when working with closed sections whose directions differ.
Segments, closing the loft, and connecting to SubD
In SubDLoft, shape segments and divisions between consecutive curves are handled separately. Natural shape segments refers to the default number of segments used in the shapes. Adjust shape segments lets you change this number. Adjusted shape segments sets the number of segments along the input curves, while Divisions between shapes sets the number used between adjacent shapes. Since the documentation does not provide a numerical recipe for these fields, avoid unnecessary complexity and test the form as needed.
The Closed option closes the loft direction when there are at least three curve inputs. When working with open curves, Corners can sharpen the corners at the ends of the first and last shapes. If the input curves contain kinks, Creases can be used to sharpen the edges at those kinks. Determine which options to use based on the structure of the curves and the intended surface shape.
When a SubD edge is used as the first or last shape, Join connects the loft to the existing SubD. The Smooth option makes the connection smooth-edged; without this option, the connection has a sharp edge. An important limitation is that Join does not support History recording. If you expect to use a History-based workflow when editing the model later, consider this limitation before choosing this connection method.
What should you consider in an architecture and visualization workflow?
SubDLoft can be a useful modeling option for architects, interior designers, and 3D artists who want to create flowing or variable forms defined by section curves as SubD objects in Rhino. Matching control points on curves, aligning edge loops, and reviewing segment settings are steps that can improve control over the model’s form. However, the source documentation provides no information about render performance, hardware requirements, licensing terms, or compatibility with other software, so no conclusions can be drawn on those topics.
Especially when handing a model off within a team, documenting the curve order, whether curves are open or closed, and the segment options used can help the next person understand the model. The lack of History support for geometry connected to an existing SubD with Join should also be factored into the editing plan. For this reason, a cautious approach is to run a short test with similar curves and review the result before creating a complex form directly in a production model.
Common mistakes
Overlooking different control point counts: Differences between curves can complicate the SubD structure and prevent the surface from passing through all the curves.
Failing to check loop alignment on closed curves: Adjust the points along the curves; use Flip or SnapToKnots if needed.
Expecting Chain to create a simple SubD from edge chains: The documentation states that this method does not produce that result. To create a simple SubD, try clicking, window selection, or double-clicking.
Expecting History recording after Join: Join does not support History; plan how you will make subsequent edits before connecting the geometry.
Sources
1 sourceSource texts are not republished; short quotes are marked, everything else is our own summary and commentary.
SubDLoft gives architecture and visualization teams working with section curves direct control over the form creation process. Reviewing curve structure and segments from the outset can help reduce topological complexity later. Since the documentation provides no ready-made settings recipe, it is safer to proceed with small test models.
For offices in Turkey, this documentation does not specify new hardware or licensing requirements and should not be used as a basis for purchasing decisions. The main considerations are that differing control point counts can complicate the output and Join does not support History. Teams would benefit from incorporating these limitations into their modeling standards.
Frequently asked questions
What does the Rhino 8 SubDLoft command do?
It creates a SubD object from selected curves that define a shape.
How do you align edge loops on closed curves in SubDLoft?
You can select the points and move them along their curves. Flip reverses the curve direction; SnapToKnots determines whether points move constrained to knots.
Does Join in SubDLoft support History recording?
No. According to the Rhino 8 help documentation, the Join option does not support History recording.
