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Bezier

The Bezier tool allows you to create a type of curve defined by off-curve control handles. Bezier curves were originally developed for computer modeling in automotive design, but are popular in many vector drawing applications. These curves provide a familiar means of generating curves, as they allow you to interactively control the amount of incoming and outgoing curvature for each control point.

You can find the Bezier tool in the Basic sub-tab of the modeling toolbox, or in the menu bar, under Geometry > Curve Palette.

To use the tool:

1.

In the Basic sub-tab of the modeling toolbox, right-click the Pen tool to reveal additional tool options, then click Bezier Curve to activate the tool.

Alternatively, you can access the tool by opening the Curve Palette, found in the menu bar under Geometry > Curve Palette.

2.

Click in the 3D viewport to position the first control point, then continue to drag the mouse cursor to create the Bezier handle.

3.

Release the mouse button to set the handle length.

Subsequent clicking and dragging draws additional control points and handles with a curve segment between each control point. Control points are always created at the intersection of the work plane and the mouse button click. The curvature of the segments between control points is defined by the Bezier handles, which are called endpoint tangent vectors.

To create straight line segments, click in the viewport without dragging. This creates control points with zero-length tangents. When you move these control points later, the corners remain sharp and the lines straight. You can see the two control point types below:

You can round sharp corners by switching to Edit mode in the Bezier tool's Properties panel. Edit mode reveals handles for the control points that you can drag out to create round corners:

For more details on the various modes, see Bezier Tool Properties.

4.

While the tool is active, you can re-position the control points by clicking and dragging them. Pressing and holding Shift moves all points to the right of the selected control point as a single unit.

Tip:  To create a closed curve, right-click on the first control point. Modo adds a curve segment between the first and last control points.

Points always move on the two axes relative to the current work plane, so rotating the viewport to change an axis may be necessary.

You can edit the handles in a similar way. Dragging on the end of one handle breaks tangency, allowing opposing handles to be different lengths and/or angles. You can restore tangency and edit both handles in unison by pressing and holding Shift while adjusting the handles.

Bezier Tool Properties

Once you drop the tool by pressing the spacebar, interactive handle editing within the tool itself is lost but you can re-activate the editing ability by selecting the curve in Polygons selection mode. This displays the editing handles. Control points along the Bezier curve can also be positioned precisely by selecting the target vertex and using the Point X, Y, Z fields of the tool's Properties panel.

The following Bezier options are available for adjusting the Bezier tool:

Bezier
Mode	There are three Bezier curve mode options: • Add - The default mode. When you click in the viewport, additional points are added to the curve. At each control point position, two handles extend out that allow you to adjust the curvature of the curve segment between vertices. While drawing, you can hover over any point or handle where it turns yellow. You can then click and drag the control point or handle to further edit the curve. Control points may be added mid-curve by selecting the preceding control, highlighting it yellow, and clicking the position where the new control point is desired (point order is defined by the initial order in which the curve was created. Press F before activating the tool to invert the order). • Edit - Click and drag any of the control points or handles along the curve to change the look to the desired shape. Pressing and holding the Shift key allows you to edit both handles of a control point simultaneously. • Delete - Click any control point along the curve to remove it from the Bezier.
Point X, Y, Z	You can assign specific X, Y, and Z values in these input fields for the currently-selected control point, allowing for finer point control.
In X, Y, Z/Out X, Y, Z	You can assign specific X, Y, and Z values in these In and Out input fields for the currently-selected (highlighted) handle, allowing for finer handle control.
Closed	Adds an automatic curve segment between the first and last control point positions, producing a closed curve.
Filled	When the Closed option is enabled, you can enable this to create a renderable flat surface defined by the outlining curve. The resulting surface can be tagged like a polygon for adding material definitions.
Make UVs	Activates auto-generation of UV texture coordinates along the curve. The generated UV values are of a single vertical line (V axis in UV), positioning all the control point vertices evenly between 0 and 1. For example, this can be useful for applying a gradient to a rendered curve. The Render Curves option is available in the Mesh Item properties.