Preferences > Construction Options

Notes

If you are using a CAD software preset, you cannot change the tolerances. They are locked to the factory settings for the CAD software.
You cannot edit or delete the original CAD package presets.
If you want to change a set of presets, use the Copy button to create a copy of the set you want to edit, then edit the copy.
Changes to the settings in this panel are always saved automatically. You do not have to click a Save button or choose Preferences > User Options > Save Options.

Construction Presets

Copy: Copy the highlighted settings profile to a new profile.

If you want to change some of the settings in one of the presets (for example, Inventor), make a copy of the preset profile, then edit the copy.
Delete: Delete the highlighted settings profile.

You cannot delete the preset settings profiles.
List of settings profiles: Click a profile to use the settings in that profile.

The preset profiles (for example, Inventor) contain the settings needed for best compatibility with various CAD systems.

Units

Linear Unit options

Scale Factor checkbox/sliders

Check this box to show Scale Factor sliders for the unit choices (Main Units, Sub Units, and Pos Units).

Use the scale factor sliders to change a unit from whole to fractional or multiple units. For example:

Set the Sub Units to Inches.
Set the Scale Factor slider below the Sub Units box to 0.125.
The sub unit is now eighths of an inch rather than whole inches.

Main Units

The unit of measurement for all linear measurements (in locators, on the prompt line and in windows).

Sub Units

The intermediate level of linear units.This is the unit of the second number when you type numbers using the m:s or m:s:p form on the prompt line. This unit is only used in keyboard input.

Pos. (positional) Units

The smallest level of linear units. This is the unit of the last number when you type numbers using the m:s:p form on the prompt line. This unit is only used in keyboard input.

Reset Grids

Set the grid spacing to 1.0 of the current Main Unit (taking into account the scaling factor, if set).

Angular Unit options

Scale Factor checkbox/sliders

Check this box to show Scale Factor sliders for the unit choices (Main Units, Sub Units, and Pos Units).

Use the scale factor sliders to change the different units from whole to fractional or multiple. For example:

Set the Sub Units to minutes.
Set the Scale Factor slider below the Sub Units box to 0.5.
The sub unit is now half minutes rather than whole minutes.

Main Units

The unit of measurement for all angular measurements (in locators, on the prompt line and in windows).

Choose Deg (degrees), Min (minutes), Sec (seconds), or Rad (radians). The default is degrees.

Sub Units

The intermediate level of angular units.This is the unit of the second number when you type numbers using the m:s or m:s:p form on the prompt line. This unit is only used in keyboard input.

Choose Deg (degrees), Min (minutes), Sec (seconds), or Rad (radians). The default is minutes.

Pos. (positional) Units

The smallest level of angular units. This is the unit of the last number when you type numbers using the m:s:p form on the prompt line. This unit is only used in keyboard input.

Choose Deg (degrees), Min (minutes), Sec (seconds), or Rad (radians). The default is seconds.

Tolerances

Fitting

Curve Fit Distance

The value and units of the maximum distance allowed between two points for the system to consider them coincident (occupying the same space).

For surface creation tools such as Rail Surface and Square, this value controls the accuracy of the fit of the surface edge to the construction curves.
For fillet surfaces, this value controls the positional accuracy of the fillet surface.
For the Stitch tool (used to stitch surfaces into a shell), this value determines which sides to check for gaps. However, the gap is actually checked against the Maximum Gap Distance tolerance (see below). If the gap is within the tolerance, the sides are joined.

Curve Fit Checkpoints

The sampling rate for curve fit constraints such as Continuity Angle and Curve Fit Distance.

Max Surf Spans

The maximum number of spans to create when building surfaces.

If a rebuild operation on a curve or surface requires adding more than the Max Surf Spans, the operation is cancelled.
If maintaining continuity requires adding more than the Max Surf Spans, the continuity will not be achieved.

Continuity

Maximum Gap Distance

The maximum distance allowed between two curves or two surfaces for the system to consider them contiguous (touching).

For the Stitch tool, this value controls whether two edges will be joined when stitching surfaces into a shell.
For the Surface continuity tool, this value controls whether common edges pass the check for gaps.

Continuity Angle

The maximum angle allowed between two surface normals for the system to consider the normals pointing in the same direction.

A smaller value gives better continuity, but usually requires tools to add more spans to the surface.

Continuity Curvature

The maximum deviation allowed in curvature.

A smaller value gives better continuity, but requires tools to add more spans to the surface.

Topology

Topology distance: Used to calculate which surface is adjacent to which surface when a tool needs to know the topology of the model. This is used by Object Edit > Dynamic Shape Modeling > Transformer Rig, Evaluate > Continuity > Surface Continuity, and Evaluate > Check Model.

Note
This should be set to a value greater than Maximum Gap Distance.

Curve on Surface/Trim

Trim Curve Fit: The maximum deviation allowed between the original curve-on-surface and trim edges.
Max Gap Between Curves: The maximum distance allowed between endpoints of different curves-on-surface for the system to consider them continuous for the purposes of defining a trim region.

In example A, the gap between the two curves-on-surface is greater than Max Gap Between Curves, so the curves do not define an area.

In example B, the gap between the curves-on-surface is within Max Gap Between Curves, so the curves define an area for the purpose of trimming.

Rational Flags

Note

Do not turn these options on unless you understand what rational geometry is and why you need it. In most cases, rational geometry is slower and harder to model with.

Primitives: Create new primitives using rational geometry.
Fillets/Round: Create new fillets and rounds (that is, surfaces created by the Fillet and Round tools) using rational geometry.
Curves/Surfaces: Create all other new curves and surfaces (that is, all curves and all surfaces that are not primitives, fillets or rounds) using rational geometry.

Fonts

Default Modeling Font Size: Choose a value from the pop-up menu to adjust the size of the font used in the modeling windows for annotations and such text.
Text Display Mode: Choose either Scale or Fixed Size. Fixed size will display at a constant size; Scale will change based on Dollying and Zooming.