Note: this post has been extensively edited on 7-JUL-2025. The new command that was formerly known as *FillSrf* has been renamed *Patch*, while the old *Patch* command is now called *PatchOld* (does not auto-complete).
Rhino 9 WIP has a completely revamped Patch command. This command takes a set surface edges, wire curves and points as input constraints to create a multi-sided patch with positional (G0), tangential (G1) or curvature (G2) continuity to selected edges, curves and points. The command refines the surface in places where the constraints are not met. This command produces better results than the old Patch (still available as PatchOld) command: better conformation to input curves, allowing the patch to be joined without naked edges, better surface smoothness and up to G2 continuity, where PatchOld only does G1.
Command flow
The new Patch command is non-linear in non-scripted, interactive mode. This means that you can start the command, select some input curves and points to view an initial patch result. While the dialog is open, you can keep using Rhino to add points, edit curves, move input patches, etc. etc. When input selected for Patch changes, the preview patch will update automatically. Finish the command by clicking [OK] in the dialog to add the result to the document.
The command also supports History and you can double-click on the result to activate the Edit mode, which re-opens the dialog and allows you to continue where you left off.
Command Dialog and Options
Constraints
Click on the [Constraints] button at the top to add/remove curves and points to the constraints. Hover over the green check-mark to reveal a red cross that will clear all constraints. The constraint curves and points will be labeled I, G0, G1 or G2 with their selected continuity. Left- or right-click on the labels to change the continuity to the next or previous continuity; Shift+left/right-click will change all contraints at the same time. Setting all constraints can also be done by clicking one of the buttons in the dialog below the [Constraints] button.
Stiffness
The stiffness will change the shape of the surface. Increasing the stiffness will remove more bending from the surface, at the cost of creating isolated spots where bending is higher, while reducing stiffness will distribute the bending more evenly over the whole surface. There are cases in which increasing the stiffness is needed to get a good result, but most of the time keeping stiffness at zero is a good choice.
Degree
The degree of the surface can be changed from 3 to 5.
Domain
The domain option is used to create a trim domain on the surface that outlines the patch. There are three options for the domain:- Untrimmed. This option is only available when the selected edges and G0 wire curves can be combined to give 4 curves and will create a four-sided untrimmed surface.
- Projected. Suitable for input curves that are more or less planar; this option is selected automatically if that is the case.
- Molded. Default in all other cases. This option will create the best trimming domain for curves that are not more or less planar.
Trim ends
Attempts to make a closed curve outline of the input curves. If that is possible, it removes dangling curve ends that do not participate in the closed outline. In other words, the selected curves do not need to meet end-to-end if this option is active.Refine
Refines the surface in places where constraints are not met, by adding more control point lines.Preview
When preview is off, options can be changed without triggering a re-calculation.UV control (expert option; expand to see details)
Options here allow for a fine control of the domain and surface structure. UV rotation will rotate the surface by the given amount of degrees. This can help to make a fit at the cost of having more of the surface not participate in the patch. U- and V-spans will increase the number of starting control points and clicking the Starting surface button will let you select a starting surface whose degree, number of control points and knot vectors are used as input.
Tolerances (expand to see details)
The position, normal and internal constraint tolerances can be set in the Tolerances fold-out.
Tolerances (expand to see details)
The position, normal and internal constraint tolerances can be set in the Tolerances fold-out.
Constraint test results
At the bottom of the dialog, you get quick feedback whether constraints have been met within tolerance. The Int, G0, G1 and G2 text will be green if the tolerance was met, red if the tolerance was not met or grey if that type of constraint is not present.
Examples
The new Patch command is able to make complex patches, like in the following three examples:
fillsrf-example-1.3dm (154.5 KB)
fillsrf-example-2.3dm (246.4 KB)
fillsrf-example-3.3dm (215.3 KB)
This third example shows the untrimmed option for the two four-sided patches, while the corner is created with the aid of the two internal curves.
These examples are also relevant for the new Patch command:
multisided-example-1.3dm
multisided-example-2.3dm
multisided-example-3.3dm
More details
The modeling is based on treating the NURBS surface as a thin membrane with elasticity and internal strain under bending. This is captured in an "energy" that the surface has, and the algorithm minimizes this energy while complying as much as possible to the positional, tangential and curvature constraints applied. This approach is also known as *variational surfacing* and is similar to what the XNurbs plug-in uses.Future developments
Note: the command is under development and its options and result may change without notice.
- “your wishes here” - let us know what works and what needs improvement
- Internal curves, points and normals as constraints
- While it is currently possible to select curves that do not form a closed loop, the results may vary and no trimming is applied.
- A more interactive user experience
- ability to change continuity during the command, currently continuties that are chosen at the start cannot be changed
- ability to add and remove curves during the command
- a dialog with command options
- History support RH-86002
- Grasshopper suppport RH-86003
- Automatic closed loop detection RH-86006
- Starting surface input RH-86009
Fingers crossed !!
