Bringing In Assemblies

This page takes a kit of parts (branches, sprigs, leaf clusters) into Natsura and checks it, so it is ready to place on a tree.

You should have Natsura installed and know your way around the Interface. Assemblies explains what an assembly is.

Place an Assembly Resource

1. Open the Assemblies menu on the toolbar and click Assembly Resource. A new one loads the built-in example kit (Filetype BGEO, branch_kit.bgeo.sc). Parts with bad pivots show red, and the node reads "Fix N bad pivots (Enter)".

Fix the pivots

Each part's pivot should sit at its base, where it joins its parent: a branch where it meets a larger branch, a leaf where it meets its stem. Rigging works out what attaches to what from these pivots.

1. With the Assembly Resource selected, press Enter. The viewport shows just the parts, with the bad ones in red. Left-drag roughly over a part from its base in the direction it points, and the pivot moves to that base.

2. The drag doesn't handle concave shapes well. Where a pivot lands in the wrong place, drag the gizmo to line it up.

3. When nothing is red, the warning goes and the node shows how many instances and assemblies it found (12 and 5 for the example kit).

Pivot Edit has the same state as a node of its own, and lists the other keys.

Check the rig

1. Press play. The parts move in the preview wind. If no part comes loose, the automatic rigging worked.

2. Set the Wind menu on the display toolbar to Strong to see the movement better, and turn on Display Rig, under Display, to see the joints. This wind is only a check on the rig, not a preview of the tree in Unreal.

Load your own kit

1. On an Assembly Resource, set Filetype to USD or BGEO and pick the file in USD file or BGEO file. You can also wire SOP geometry into its first input instead. A kit that comes already set up, like the oak kit here, needs no pivot fixes: press play and it moves straight away.

2. Instances of the same geometry must share a name. Pieces sets which attribute holds it (name by default).
3. If the kit is the wrong size or lies on its side, set Uniform Scale and Rotate. Natsura works in metres, so a kit exported in centimetres, for example, needs a Uniform Scale of 0.01.

Add materials

1. Place a Surface Resource and pick the kit's texture in Colour. On the Assembly Resource, open Materials and drag the Surface Resource node onto Surface Resource 1. The parts take the texture.

2. For a kit with several materials, such as bark and leaves, click + next to Materials to add a row per material. Group on each row picks the faces it applies to: leave it empty for the whole kit, or pick a group. The shape groups (cardish, tubeish, needleish, blobish) are a guess from each piece's shape, so check the result in the viewport.

Turn parts that face the wrong way

Some libraries mix parts that point different ways, for example small sprigs that face up while the rest face down. Turn them once here and every decoration downstream places them the right way round.

1. Click Edit Assembly in the strip at the top of the Assembly Resource, or put an Assembly Edit on the wire after it, and press Enter. Click a part, press R for the rotate gizmo and turn it. Parts are turned one at a time.

Another way is to split the library into groups and give each its own decoration.

Next

The parts are now a rigged library. Decorating With Assemblies places them on a tree, and Assembly Resource covers every setting.

Status

The footage was recorded on a 0.7.3 preview. Assembly Edit has no box selection yet.