Terrafold

Chapter 5

Keeping models clean

So far everything you drew is loose geometry, and loose geometry sticks to whatever it touches. That was useful for folding the roof, but in a real project you want the shed, the planters and the fence to stay separate. This chapter explains why groups and components exist, and when to use which.

When stickiness gets in the way

Imagine you draw a compost bin against the side of the shed. Its side face lands on the shed wall and its edges join the wall's edges. Now move the bin away: the shared edges come along, and the wall is pulled out of shape. Triple-click the bin to select it, and you select the shed too, because everything connected is one surface.

Loose geometry shares edges with whatever it touches (left). Put each part in a group, and they touch without merging (right).
Figure 5.1 Loose geometry shares edges with whatever it touches (left). Put each part in a group, and they touch without merging (right).

The fix is to wrap each separate thing in a group or a component as soon as it is finished. Geometry inside a group sticks only to other geometry in the same group.

Group the shed

  1. Press Space for the Select tool.
  2. Drag a selection rectangle from left to right around the whole shed. A left-to-right drag selects everything that lies fully inside it.
  3. Choose Edit ▸ Make Group.
  4. In Entity Info, type Shed as the instance name.

Click the shed now and it is selected as one object, with a box around it. To change something inside, double-click it: you are in the group, the rest of the model fades, and you edit as before. Click outside it, or choose Edit ▸ Close Group or Component, to leave.

Groups and components

A component is like a group, with one difference that matters: copies of a component share their contents. The contents are the component's definition; each copy you place is an instance of it. Change the definition through any instance and all of them change.

Groups are independent copies. Component instances all show the same definition.
Figure 5.2 Groups are independent copies. Component instances all show the same definition.

Use a group for a one-off: the shed, a wall, the terrain. Use a component for anything that repeats: planters, fence panels, posts, windows, chairs. Components also keep files small, because the geometry is stored once.

Planters as a component

  1. Select the planter (drag around it) and choose Edit ▸ Make Component (G). Name it Planter.
  2. Move a copy 1.2 m to the right: Move (M), press Ctrl, click a corner, move along the red axis, type 1.2, Enter.
  3. Type 2x and press Enter. You have three planters.
  4. Make the pot a component too, named Pot.

Now edit one planter: double-click it, Push/Pull its rim up 3 cm, and close it. All three get the taller rim.

Make Unique

Sometimes one copy should differ. Select the third planter and choose Make Unique on the Group context tab (or the button in Entity Info). It gets its own definition, called Planter#1. Edit it, push its rim up another 15 cm, and only that one changes.

Three planter instances (left). One edited, all three change (middle). The third made unique and edited on its own (right).
Figure 5.3 Three planter instances (left). One edited, all three change (middle). The third made unique and edited on its own (right).

Entity Info and the Outliner

Entity Info shows what is selected and lets you change it: for a component, its tag, material, instance name, definition name, how many instances there are, position, scale and buttons for Make Unique, Reset Scale and Options.

Entity Info for a planter: a component with two instances (the third was made unique).
Figure 5.4 Entity Info for a planter: a component with two instances (the third was made unique).

The Outliner (Window ▸ Default Tray ▸ Outliner) lists every group and component as a tree. Component instances show their definition in angle brackets. Click a row to select it, double-click to rename, use the eye to hide and the lock to protect it, and drag a row onto another to put it inside.

The Outliner of the project: the Shed group, the planters (one of them the unique Planter#1), the pot and the fence panels.
Figure 5.5 The Outliner of the project: the Shed group, the planters (one of them the unique Planter#1), the pot and the fence panels.

The fence

The back of the garden gets a fence of six panels, each a post and a board. You make one panel as a component and copy it.

  1. Draw a 10 cm by 10 cm rectangle at the left end of the back boundary and Push/Pull it up 1.65 m: the post.
  2. Draw the board as a rectangle standing against the post (start on the post's side face, it lies on that plane): 1.8 m wide, 1.5 m high, starting 5 cm above the ground. Push/Pull it 2 cm thick.
  3. Select the post and the board and make them a component named Fence panel.
  4. Move a copy 1.9 m along the red axis and type 5x.
One fence panel: a post and a board, made into a component.
Figure 5.6 One fence panel: a post and a board, made into a component.

The Components panel (Window ▸ Default Tray ▸ Components) now lists Planter, Pot, Planter#1 and Fence panel with how many of each the model has. Click one, or drag it into the viewport, to place another instance.

The Components panel: every component in the model with a thumbnail and a count.
Figure 5.7 The Components panel: every component in the model with a thumbnail and a count.
The project after chapter 5: the shed is a group, the planters, pot and fence panels are components.
Figure 5.8 The project after chapter 5: the shed is a group, the planters, pot and fence panels are components.