Editing Lathe Curves

Boxshot provides a simple built-in curve editor for lathe objects. Although you may use external applications like Adobe Illustrator to edit curves, the built-in editor is more than good enough for everyday work.

Some Notes Before We Start

Boxshot needs a single, solid curve to make a lathe object. The built-in editor does not allow you to make two independent curves and you will get an error if you try to import them from another application.

The curve may have several segments. A segment is a piece of curve between two control points. Each segment may have its own material and can be either single- or double-sided.

All the segments are connected using control points. A control point can be either hard or smooth. You can add and remove points, but you can't remove the very last segment.

Lathe Editor

Here is the lathe editor window (click to see the full view). The tutorial is based on the Windows version of Boxshot, but the OSX user interface is absolutely the same:

The toolbar at the top has the "presets" menu where you can load and save your curves to SVG or use the predefined ones. Beside "presets" is the "tools" section, where you can switch between selections, adding and removing nodes. There are also zoom buttons at the right.

The curve itself occupies the main part of the screen. Boxshot adds a reflection, so you can better understand the shape of your lathe object while editing it. All the measurements are in millimeters, so you can make exactly the shape you need.

Navigating Around

Click and hold the left mouse button, then drag the mouse to move the scene around. Use the mouse wheel to zoom the scene in and out.

Moving Points

Click a point to select it and you will see the toolbar and the point itself have changed:

You can only select one point at a time. For the selected point Boxshot shows two handles that allow you to control the curve at that point. The toolbar at the top allows you to switch between smooth and hard points and manually edit the point coordinates.

Try to move points and their handles to see how the curve changes. You can always undo any modification by pressing Ctrl-Z (or Cmd-Z on Mac).

Adding And Removing Points

You can easily remove the selected point by pressing "Del" on the keyboard. Use the delete mode to remove several points at once: click the "Deleting" icon then click the points you want to delete one by one. You can delete as many points as you want:

Use the "adding" tool to add points. Activate it and click somewhere on the curve to add a point there:

The point has been added:

Boxshot tries its best to keep the curve shape the same while adding points. You can add as many points as you need by splitting the existing curve.

Note that you can't add points outside the curve, so if you want to extend the curve, you need to move its end further and add points to the last segment.

Assigning Materials

You can also click a segment to select it. The toolbar changes to display the selected segment's parameters:

The materials toolbar contains a material selector and a single/double-sided switch. To assign a material, simply click the material selector and type the name you need. You can see all the curve's materials in the drop-down list, so you can quickly re-use materials.

Switching between single and double-sided allows you to decide how the segment will appear in 3d. Single-sided segments are visible from one side only, while double-sided segments are visible from both sides. In most cases single-sided segments are OK. Double-sided segments can be used for creating labels on glass bottles, so you can see both sides of the label and assign separate materials to each side.

Texture Mapping

Boxshot wraps the U texture coordinate around the shape while rotating the curve. The V coordinate goes from the bottom to the top and crosses control points if the next segment has the same material. If the material is different, the V coordinate starts from zero on that segment.

Basically, Boxshot fits vertical texture mapping into contiguous segments that share the same material. This allows you to make a bottle label with correct mapping, for example, simply by assigning another material to its segment(s).

SVG Files Support

You can save and load curves to and from SVG files. This is useful for editing curves in external applications or for keeping them for future re-use.

You can assign materials to segments in Illustrator by changing path names.

Useful Options

Click the "OK" button when you finish editing the curve. Boxshot will then generate a lathe object of your curve. Depending on your curve you may need to adjust some of the options in the "Lathe" panel at the right. Here is a brief list of options and their effects:

Top/bottom cap - these caps close both ends of your shape if the ends of the curve are not at the center of rotation.
Align curve to center - this option moves the curve as close to the center of rotation as possible.
Generate back faces - makes all the segments double-sided.
Flip normals - invert the shape by making its back side the front and vice versa.
Flip texture mapping - flips the mapping vertically, which is useful for upside-down curves.

There are more options there, but these are the most important ones.

That's All

Now you can edit lathe curves and create various objects like bottles, cans, and glasses. Good for you :)