Modelling with primitives

The Build mode of the asset editor assembles parametric primitives, the Roblox Studio way. Each part has a shape, a position, a rotation, a size and a PBR material; parts combine through boolean operations and attach to bones so they can be animated.

Create a Build asset#

A built asset is a VoxelAsset of kind: 'mesh': instead of a voxel grid it carries a primitives[] list. Its world scale is picked among ¼, ½, 1, 2 and 4.

1. Add the asset

   On the Build step — or in the asset editor if it is already open — click + Build. A project holds at most 96 assets.

2. Add parts

   Click a shape under “Add a part”. If a part is selected, the new one appears next to it, with its material and bone.

3. Place with the gizmo

   Click a part in the viewport to select it, then W move, E rotate, R scale. Hold Shift to snap.

4. Fine-tune with numbers

   The part panel shows position, rotation (degrees) and size on three axes. The minimum size is 0.05.

Starter kits#

Five kits add a small ready-to-edit build in one click, showing booleans and profiles in context:

Shapes#

Every geometry is built unit-sized and centred, then scaled by the part’s size field. Eleven shapes are available (PrimitiveShape):

Extrude and lathe profiles#

The extrude and lathe shapes read the profile field (ProfileId). The panel only offers the profiles that fit the chosen shape.

Bevel#

The Bevel slider shows for rounded (0 to 0.5, the corner radius in world units, capped at half the smallest dimension) and extrude (0 to 0.2, the chamfer thickness on the profile edges).

Boolean operations#

A part’s op field says how it combines with the parts listed before it on the same bone. Parts are evaluated in order: the first is the base, each next one is added, subtracted or intersected. The computation uses three-bvh-csg and produces one mesh per bone.

[
  { "id": "wall", "shape": "box", "pos": [0, 1, 0], "rot": [0, 0, 0], "size": [4, 2, 3],
    "material": { "color": "#e8e4dc", "roughness": 0.9 } },
  { "id": "door", "shape": "box", "pos": [0, 0.7, 1.5], "rot": [0, 0, 0], "size": [0.9, 1.4, 0.4],
    "material": { "color": "#3a3733" }, "op": "subtract" }
]

PBR materials#

Each part carries a Material. Eight presets (Plastic, Matte, Metal, Gold, Glass, Neon, Wood, Stone) replace the material while keeping the part’s colour; the sliders then set each value.

Materials and render style#

How a material renders depends on the world’s style (Moods). Roughness and metalness only matter in Low poly and Realistic; Voxel and Toon keep colour, glow and opacity.

Textures#

The PBR texture picker loads the 46 texture sets of the library (Poly Haven, CC0). Picking one fills map, normalMap and roughnessMap at once and sets the repeat to 2 if it was unset. “none” removes all three maps.

Bones and animation#

A built asset’s bones are its parts: a pivot, a name and an optional parent. A primitive attached to a bone (its part field) turns around that pivot when a clip plays. New bone from part creates a bone whose pivot sits at the base of the selected primitive and attaches it.

“Quick animation” applies the same presets as the Animate surface; they move bones by name (leg, arm, wheel…). See Animation.

Reference: Primitive#

What Build does not do#