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Shape primitives

Shape primitives

· 3 min read
Dragos
Balaur

Ten 3D primitives and six 2D ones, bezier paths that extrude, revolve and sweep, booleans in both dimensions, a cloner, and text as geometry. Every one of them is a mesh.

  • The primitives are torus, pyramid, prism, tube and rounded cuboid, with ellipse, star and ngon in 2D. segments, rings, sides and corner_radius work on all of them.

    The primitives row

  • path2d and path3d assets extrude with a bevel, lathe, sweep along a rail, or stroke with a join, a cap and a taper.

    An arch extruded, a goblet revolved, a rail swept

    Polylines with round, miter and bevel joins, three caps, a tapered gradient, and two closed squares

  • boolean3d and boolean2d run over a node's children: union, difference, intersection. Operands stay editable, moving one recomputes, and booleans nest.

    Union, difference and intersection of a cube and a ball

  • shape2d gained ellipse, star and ngon, and boolean2d joins, cuts and intersects filled outlines. The 2D booleans run on i_overlay, in fixed-point integers, so every platform gets the same vertices.

    Ellipse, star, ngon and capsule; a rect and a circle joined, cut and intersected

  • A cloner is linear, radial or grid, and seed and random scatter the copies. A thousand copies are one draw call, custom materials included.

    A row, a ring and a scattered grid

  • kind = "text" on a mesh asset turns a word into geometry, counters kept as holes, sized in world units, sitting on its baseline.

  • Vertex colours and morph targets both survive a glTF import. A morph weight is a property, so a clip drives it as mesh/morph.<name>, and vertex colours reach a material with features = { vertex_color = true }.

    A word as a mesh, and a triangle coloured per vertex

One mesher​

  • A collider fitted to a torus is a torus.
  • A ray picks the shape that is drawn.
  • Headless tests check every mesh is closed and outward-facing, with the exact volume a boolean should have.
  • Deterministic: libm for the curves, and a BSP of dot products and lerps.
  • The meshers are the engine's own: core builds the triangles, physics fits its colliders to them.
[[assets]]
id = "ring"
type = "mesh"
kind = "torus"
radius = 1.1
tube_radius = 0.28

[nodes.mesh]
source = "#ring"

[nodes.collider3d]
kind = "trimesh"
mesh = "#ring"

examples/objects has five rows, one per category, then the 2D layer. It runs in the browser. The manual and the generated asset and component references have the keys.