Decorating With Assemblies

This page places the parts of an assembly library on a tree with an Assembly Decoration and shapes the canopy they make.

You need a tree with at least one Grow (Your First Tree) and a checked library from an Assembly Resource (Bringing In Assemblies).

Place the decoration

1. Choose Assembly Decoration from the Decorate menu and wire the Assembly Resource into its first input. Until a Grow carries it, the parts sit on a preview tree inside the node. The Simulate selector on the display toolbar switches it between trunk, monopodial and sympodial.

Choose where parts spawn

1. Spawn at picks the points that get a part: Tips, Intersections, Internodes and Roots, in any combination. Mask is the chance each point keeps its part; lower it and the canopy thins at random.

2. Turn on Internodes to fill the canopy towards the middle. For more points along each internode, turn on Divisions, or set Mode to Distance and use Step Length.

The clip also raises Scale, which suits the preview tree. On your own tree, a kit made at real size usually wants Scale at 1; if the canopy then looks sparse, the tree needs more branching to carry the parts. For games, scaling parts up 1.5 to 2 times can read better at a distance.

Choose parts with traits

A trait is an attribute that lives both on the tree's spawn points and on the parts, and each point takes the part whose value is closest. Traits covers the matching.

1. Click Add Selection Trait and choose Create New. The new trait gets a Weight slider.

2. Press Launch (Enter) to open the chart beside the tree. Drag parts from the row below onto it, then move Weight: the part closest to the Weight is picked. Shift-drag selects several parts and a middle-mouse drag lines them up. Reset sends every part back off the chart. Classify Parts, in the trait row's menu, opens the chart too.

3. Most traits come from the skeleton. Add Selection Trait lists the attributes the tree already has, such as height. A skeleton trait has a Range, set from the tree, instead of a Weight. Put large parts at one end of the chart and small parts at the other, and the parts change from the base to the top.

4. Add a second trait, such as elevation_angle, and the chart takes it on its other axis. Put small parts at the low end of elevation_angle and they go on branches that point down.

Bend parts with effectors and maps

1. Click Add Effector and add a Gravity Effector. With a plain value it turns each part as a whole. Use the map button next to the effector's Scale, choose Map from attribute, u, then Self: u runs along each part's rig, so the part now bends along its length.

The preview build in the clip lists the attribute as assembly_u; in 0.7.3 it is u.

2. With that map selected, click Map Blend on the toolbar, then Insert (right). Wire a second map, for example from height, into the Map Blend's second input and set Mode to Multiply. The bend now changes from the base of the tree to the top. Mapping covers chains of maps.

Thin the canopy

1. Map Mask from u to thin by position rather than at random. Parent u reads how far along the parent branch a part sits; Self reads the branch it spawns on. Shape the ramp to keep more parts towards the edge of the crown and fewer inside.

2. Raise Prune, at the bottom of the node. It looks at how dense the canopy is and removes from the densest areas, and it removes pieces inside each part rather than whole parts.

Mask and Prune work together, but in opposite directions: a high Mask keeps parts, a high Prune removes them. A map made for Mask needs its ramp flipped before it does the same job on Prune. Prune also responds to every change in shape, so set it to 0 while you tune effectors and bring it back at the end.

Put it on the tree

1. Drag the Assembly Decoration into an empty slot under Decorations on the Grow whose branches should carry the parts, or select the Grows and choose Assembly Decoration from the Decorate menu. The parts appear on the real tree, the Simulate selector can show it, and maps can read the tree's attributes.

Next

Assembly Decoration covers Transform, the effector modes and Export Rig. To take the tree to Unreal, see Take Your Tree to Unreal.

Status

The footage was recorded on a 0.7.3 preview. Gravity Effector and Map Blend are marked experimental. Parts on the chart sometimes draw wrongly; toggling the display flag fixes it.