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Creating arcs

Creates a curved polygon by Spline.

\spline

You can use this command to:

Create a spline by points

Convert a polygon to spline

Edit a spline

Draw a spline by point

To create a spline point by point, first indicate all the vertices to the tangent points of the spline. A polygon is created as you add the subsequent points. It serves as a visual support to see the overall shape of the spline before it is created.

Press "Enter" to draw the spline and erase the polygon.

Convert a polygon to spline

Indicate the polygon to convert.

A spline drawn or converted in this way can then be used as a simple polygon. Thus, you can use it as the area of the surface to calculate, or color, or as a base for obtaining simple volume.

HINT: To fill the spline with a color using the \fill command, see chapter 8-14 of volume. To use this spline in the area to calculate surface using the \psurf command, see chapter 34-70 of volume 3
To use this spline to generate a solid using \p3d, command see chapter 4-20 of volume 1

Edit a spline

Choose the "Edit" option from the "Create/Edit spline" (\spline) command, and then choose one of the following options:

Add an edge handle

Add a handle

Delete handles

Move handles

Close a spline

Customize a spline

Convert to a polygon

 IMPORTANT:

In certain options, the vertices of the spline are displayed temporarily as points. You can set their size using the command: \pntsiz.

If you fail to end the edit spline operation correctly, these points will remain on the screen. You can simply erase them by using the command to delete the help lines (\hdel).

Add an edge handle

Indicate the spline

Indicate the edges to which the handles should be attached

Click on the position where the new edge handle should appear.

Add a handle

Indicate the spline

Indicate the two handles, displayed in the form of a dotted cross, between which a new vertex has to be inserted.

Click on the position where the new vertex should appear.

Delete handles

Indicate the spline

Indicate successively all the vertices you wish to delete. Make sure that the handles of the polygon displayed in the form of dotted cross, are indicated correctly. Then, press "Enter" to continue.

 NOTE: The opening/closing of the spline is not affected by this command.

Move handles

Indicate the spline

Indicate successively all the vertices you wish to delete. Make sure that the handles of the polygon displayed in the form of dotted cross, are indicated correctly. Then, press "Enter" to continue.

Define the vector of displacement between the two points.

Close a spline

Indicate the spline…

Customize a spline

Indicate the spline.

This option displays the following dialog box to smoothen a spline:

Convert to a polygon

You can use this option to convert a spline to a polygon.

NOTE: It is recommended to reduce the smoothening of a spline before converting it to a polygon, as the polygons having too many points are difficult to manipulate and they create solids with too many faces.

IMPORTANT: If you try to modify a spline with a geometry that was changed using tools different than the ones mentioned above, then it will automatically be converted in a polygon. This applies also to a spline included in a set or expanded along a simple solid. The simplest method to use a spline as a polygon is to convert it to polygon before any modification.