Modeling Create geometry Create ball corner surfaces > Create a ball corner surface between fillets

Build corner (tertiary) surfaces

How to create surfaces that achieve smooth transitions between multiple fillets at corners.

Create rounded edges and corners

Create surfaces that round off the edges and corners between existing surfaces.

To create fillets along edges only

Choose Surfaces > Round .
Select an edge shared by two surfaces which meet at an angle.

The common edge is highlighted in green with two blue squares indicating the end points.

A radius manipulator with a radius value appears on each edge.

Click on the manipulator handles to move it or change the radius value (See Using the manipulators). You can also type a new radius value through the keyboard.
Click on the edge to add extra radius manipulators at those locations and adjust the radii.

This will set the fillet radius at those points. You can specify as many radii along an edge as you want.

Hold and click on an edge or radius to remove it.

Repeat steps 2 to 4 for any number of shared edges on your model.

If two edges are tangent continuous, they are treated as a single edge and a single fillet is built.



Press the Build button.

Fillet surfaces are built along each shared edge. All new surfaces are grouped under the same DAG node.



You can still modify the radius manipulators and press Build again to rebuild the surfaces.
If you need to select extra edges or deselect some edges at this point, press the Revert button.

The fillets are removed and surfaces are untrimmed. You can then select/deselect edges (by holding the key) then press Build again.

Notes on variable radius fillets

You can add as many radius manipulators as you want to set the radius of the fillet at several point along the edge.
Even if you do not place radius manipulators at each end of an edge, the fillet will extend from one end of the edge to the other. The fillet radius at each end of the edge will be the same as that of the outer radius manipulators.



If two or more edges are tangent continuous, they are treated as a single edge. Creating a smooth variable radius fillet across the surfaces then requires only two radius manipulators (rather than one for each edge). However, the fillet will be made up of a separate surface for each edge.

To create round corners

Choose Surfaces > Round .
Select three or four edges (each shared by two surfaces) that meet at a corner.

The shared edges are highlighted in green with blue squares indicating the end points.

A radius manipulator with a radius value appears on each edge.

A corner shape manipulator appears at the corner.



Click on a radius manipulator handles to move it or change the radius value (See Using the manipulators). You can also type a new radius value through the keyboard.
Click on an edge to add extra radius manipulators at those locations and adjust the radii.

This will set the fillet radius at those points. You can specify as many radii along an edge as you want.

Hold and click on an edge or radius to remove it.

Click on the corner shape manipulator to toggle between the different corner types (see Using the manipulators).
Repeat steps 2 to 5 for any number of corners on your model.

If two edges touch, they will be treated as a single edge and a single fillet will be built.

Press the Build button.

Fillet surfaces are built along each shared edge, and corner surfaces are built at the corners between fillets. All new surfaces are grouped under the same DAG node.



You can still modify the radius manipulators and press Build again to rebuild the surfaces.
If you need to select extra edges or deselect some edges at this point, press the Revert button.

The fillets and corner surfaces are removed, and surfaces are untrimmed. You can then select/deselect edges, then press Build again.

To create mitered corners

To successfully create a mitered surface, one surface is common to both edges; the other two surfaces must intersect.

Choose Surfaces > Round .
Select two edges that meet at a corner.

The shared edges are highlighted in green with blue squares indicating the end points.

Radius manipulators and a corner shape manipulator appear.



Adjust the radii on the two edges as desired.
Click on the corner shape manipulator to toggle between Sharp and Blended corner treatment.
Press the Build button.

Four surfaces are built: two fillets and two surfaces at the corner.

If one of the two edges has a radius of 0.0, no corner surfaces are built, only a single fillet.



You can still modify the radius manipulators and press Build again to rebuild the surfaces.
If you need to select extra edges or deselect some edges, press the Revert button.

The fillets and corner surfaces are removed, and surfaces are untrimmed. You can then select/deselect edges, then press Build again.

Using the manipulators

> Radius manipulator

The radius manipulator appears when you click on an edge. It has two handles, as shown above.

Click and drag the small triangle to move the manipulator along the edge.
Click and drag the arc to change the radius value (or use the keyboard to enter an exact value).

Holding the key and clicking on a radius manipulator removes it.

> Corner shape manipulator

This manipulator can have one of six possible shapes:

Clicking on it will toggle it between all the possible choices for the corner geometry. The shapes available depend on the radii of the fillets incident on the corner.

This manipulator only appears when creating corners.

For more information on the different corner types, see Options in Surfaces > Round .

What if...?

] The round operation fails?

Make sure the radii are not too large for the surfaces.
Make sure the surfaces don't have internal tangent discontinuities (caused my multiple knots).
See Troubleshooting trimmed surfaces

Create ball corner surfaces

Create a ball corner surface between three fillets and a primary surface.

This tool simplifies the task of creating ball corners.

Given the following conditions:

Three transitional surfaces (fillets) intersect at a corner with a primary surface.
Two boundaries (or curves on surface) on the primary surface overlap the boundaries of two different transitional surfaces.

the following steps will produce a clean result.

Create a ball corner surface between fillets

Choose Surfaces > Ball Corner
Select the three intersecting transitional surfaces.
Press the Go button.
Select the primary surface.
Press the Go button.

The transitional surfaces are highlighted in purple, the primary surface is highlighted in yellow, and small red arrows appear, indicating the intersection points.



If more than two intersections are found, you must click on two of the arrows to specify the intersections that will correspond to two corners of the ball corner surface, and then press the Go button.

The input surfaces are trimmed at their intersections, the ball corner surface is built, and the option box pops open.



Adjust the Pivot Curve Length Ratio (to shrink or expand the top edge of the ball corner).
Choose a level of Continuity and turn on Continuity Check.
Turn on Explicit Control and use the Explicit Control sliders to adjust the degree and number of spans (in both U and V direction) on the ball corner until the desired continuity is achieved. Or just try increasing the Max. New Spans value.

You will only see the Max. New Spans option if Explicit Control is off, and Continuity is Tangent or Curvature.



Every time the value of an option changes, the curves on surface that were created on the input surfaces update, the surfaces are re-trimmed (if needed), and the ball corner surface is rebuilt (if Build Surface is turned on).

The ball corner surface is also rebuilt if the input fillet surfaces are modified.

See Troubleshooting trimmed surfaces