Working with Several Bodies

A Kapy document holds as many solid bodies as you like. How you split a model into bodies, and when you merge them, decides how easy the file is to edit for the rest of its life.

Keep them separate, join them late

Two habits keep a multi-body document editable.

Model distinct things as distinct bodies. A hinge and its pin, a case and its lid, a bracket and the boss it carries: each keeps its own history and can be edited, hidden, exported or thrown away without disturbing the others.

Join at the end, not as you go. An extrude set to Add joins as it builds, which is fewer clicks and a worse document. From that moment the two shapes are one, and changing either means editing a feature buried further up the tree. Build them separately and finish with a Union. That costs one step and leaves both halves editable.

The exception is the obvious one. When the second shape only exists as part of the first, a rib on a wall or a boss on a plate, use Add, because there was never a second thing.

The active body

One body is active at a time, and a new feature attaches itself to the active body when nothing else says otherwise. The active body decides where your next extrude lands.

Double-click a body in the viewport to make it active. That is the whole interface: double-clicking makes a body active as well as selecting it, there is no dropdown to set it, and a single click only selects.

The active body survives a rebuild as long as it does. It is only re-chosen when the body it pointed at is gone, consumed by a boolean or orphaned by a deleted feature, and then it falls to the newest survivor.

If a new feature attaches itself to a body you did not expect, check which one is active. Double-click the body you meant, then build the feature again.

Names, colours, visibility

The Bodies window is where a body becomes recognisable rather than "Body 4".

• Rename one and the name sticks. The name is the body's own: renaming a body does not rename the timeline step that produced it, and renaming a step does not rename a body. A boolean does not even make a body — its result lands on the body it was aimed at, which keeps the name it already had.
• Colour comes from a palette of sixteen, handed out in order, so a document with several bodies is legible from the first one. Override it from the swatch, and the choice survives every rebuild.
• Hide a body and it stops being drawn and stops being exported. It still takes part in the model itself: it is still cut, still fused, still in the way of a boolean. Hide a body to declutter the view, not to park a body you still want in the file you download. The one exception is a print support: it is real printed material, so it goes into an STL whether it is hidden or not.

Open the Bodies window and show every body you want before you export. A hidden body is simply missing from the STL or STEP you get back, and nothing warns you.

Bodies a cut hands you

Not every body is one you asked for. A removal that takes a body apart — a Subtract, an Intersect, a Clearance Cut, or an extrude or push face set to cut — commits one body per piece, because two pieces of material that no longer touch are two parts to the Bodies window, to an export and to the slicer.

The biggest piece is the body you were editing, with its name, its colour and its visibility intact. The others follow its name: Bracket (2), Bracket (3), and so on, each taking the next colour from the palette. From there they are ordinary bodies, and a rename or a recolour you give one survives every rebuild. They belong to the step that separated them, so deleting that step takes them with it.

A union never does this. Two bodies fused when they do not touch stay one body with two lumps, which is how a pair of separate parts gets grouped into one.

If a body you did not expect turns up in the list after a cut, that is what happened: the cut went further than you thought and the part came apart.

Deleting

There is no delete on a body. A body exists because a feature made it, so get rid of it by deleting the feature in the timeline that produced it.

See also

• Union and Intersect: joining bodies at the end
• Subtract: and removing one from another
• Saving Your Work: what leaves the document when you export