RefMesh

Page Info

• Audience: Intermediate

• Prerequisites: basics of Geometry and reconstruction workflows

• Time: 15 minutes

• Output: Shared reference-mesh workflows (Level 2 concept page)

This page focuses on shared reference-mesh workflows (RefMesh + Geometry). For the procedural extrusion counterpart (ExtrudedTubeGeometry, extrude_*, lathe_*), see Procedural / Extrusion Geometry. For the high-level attribute-driven realization layer, see Prototype Mesh API.

Reference Mesh Design Philosophy

Most plants contain many similar organs - think of hundreds of leaves on a tree that share the same basic shape but differ in size and orientation. PlantGeom leverages this biological pattern through its reference mesh approach:

1. Define a single reference mesh for each organ type (e.g., a generic leaf shape)

2. Apply transformations (scaling, rotation, translation) to position each instance

This approach offers significant benefits:

• Memory efficiency: Store one mesh instead of hundreds of copies

• Smaller file sizes: OPF files store only unique reference meshes plus transformations

• Performance: Operations can be applied to reference meshes once rather than to many instances

For highly specialized shapes that can't be derived from a reference (like wheat leaves with complex curvatures), PlantGeom can still use direct mesh representations.

Where RefMesh fits in the API

RefMesh is the shared geometry asset in PlantGeom.

It is not the same thing as a prototype:

• RefMesh stores one canonical mesh plus metadata

• a prototype tells PlantGeom how to realize node geometry from that asset and from node attributes

This means:

• use RefMesh when you want to create, inspect, cache, import, or manually attach shared mesh assets

• use the Prototype Mesh API when you want PlantGeom to turn Length, Width, Thickness, and other node attributes into final geometry automatically

Quick chooser

If you want to...	Use
Reuse one mesh asset manually with your own transforms	RefMesh + Geometry
Build a shared organ asset once and cache it	RefMesh
Assign one geometry to one node for debugging	RefMesh + Geometry
Rebuild many nodes automatically from MTG attributes	a prototype built from a RefMesh
Keep an imported mesh exactly as-is during reconstruction	RawMeshPrototype

Minimal comparison

Manual / low-level:

node[:geometry] = Geometry(
    ref_mesh=leaf_refmesh,
    transformation=compose(Translation(0.0, 0.0, 0.8), LinearMap(RotZ(pi / 4))),
)

High-level / attribute-driven:

prototypes = Dict(
    :Leaf => RefMeshPrototype(leaf_refmesh),
)

rebuild_geometry!(mtg, prototypes)

Both are valid, but they solve different problems:

• the first gives you total manual control

• the second lets PlantGeom realize many node instances consistently from attributes

Overview

RefMesh is PlantGeom's reference geometry container. It stores one canonical mesh plus metadata (material, normals, optional UVs). Node geometries then reuse the same reference mesh with per-node transformations.

This is why RefMesh remains the right low-level building block even now that PlantGeom also has prototypes:

• a RefMesh stays immutable and shareable

• many nodes can point to the same mesh asset

• you can use the same RefMesh directly in manual geometry or wrap it later in a RefMeshPrototype

Structure

A RefMesh contains:

• name: reference mesh name.

• mesh: GeometryBasics.Mesh (triangular mesh).

• normals, texture_coords, material, taper metadata.

MTG Integration

Geometries in PlantGeom are attached to nodes in a Multi-scale Tree Graph (MTG) that represents plant topology:

# Attaching geometry to an MTG node
node.geometry = Geometry(ref_mesh=some_ref_mesh, transformation=some_transformation)

This is the direct/manual path. If instead you want the MTG attributes themselves to drive geometry realization, keep the RefMesh as the asset and wrap it in a prototype during reconstruction.

Create a RefMesh

From Vertices and Faces

mesh_vertices = [
    Point(0.0, 0.0, -0.5),
    Point(1.0, 0.0, -0.5),
    Point(1.0, 0.0, 0.5),
    Point(0.0, 0.0, 0.5),
]

mesh_faces = [
    Tri(1, 2, 3),
    Tri(1, 3, 4),
]

plane = GeometryBasics.Mesh(mesh_vertices, mesh_faces)
ref_mesh = RefMesh("plane", plane, RGB(0.2, 0.7, 0.3))
plantviz(ref_mesh)

From a Generated Mesh

sphere_mesh = GeometryBasics.mesh(GeometryBasics.Sphere(Point(0.0, 0.0, 0.0), 1.0))

sphere_refmesh = RefMesh("sphere", sphere_mesh, RGB(0.7, 0.4, 0.3))
plantviz(sphere_refmesh)

From AMAP-Style Extrusion (Leaflet/Midrib)

PlantGeom includes an AMAP-style extrusion helper (section profile swept along a path), inspired by AMAPStudio's ExtrudeData/ExtrudedMesh pattern.

leaflet_section = leaflet_midrib_profile(; lamina_angle_deg=40.0, scale=0.5)
leaflet_path = [
    Point(0.0, 0.0, 0.0),
    Point(0.3, 0.0, 0.05),
    Point(0.7, 0.0, 0.10),
    Point(1.0, 0.0, 0.12),
]

leaflet_refmesh = extrude_profile_refmesh(
    "leaflet_extruded",
    leaflet_section,
    leaflet_path;
    widths=[1.0, 0.9, 0.7, 0.45],
    heights=[1.0, 1.0, 0.9, 0.75],
    torsion=true,
    close_section=false,
    cap_ends=false,
    material=RGB(0.15, 0.55, 0.25),
)

plantviz(leaflet_refmesh)

Circular Tube Helper (makeCircle-style)

For axis-like organs, use the dedicated circular section helper:

tube_path = [
    Point(0.0, 0.0, 0.0),
    Point(0.3, 0.05, 0.02),
    Point(0.7, 0.08, 0.05),
    Point(1.0, 0.10, 0.08),
]

tube_mesh = extrude_tube_mesh(
    tube_path;
    n_sides=10,
    radius=0.5,
    radii=[1.0, 0.85, 0.7, 0.55], # taper
    torsion=true,
    cap_ends=true,
)
tube_refmesh = RefMesh("tube_extruded", tube_mesh, RGB(0.55, 0.45, 0.35))

plantviz(tube_refmesh)

Path Interpolation Helpers (makePath / makeSpline)

These helpers mirror AMAPStudio utilities and are useful to build smooth centerlines before extrusion:

key_points = [
    Point(0.0, 0.0, 0.0),
    Point(0.2, 0.1, 0.05),
    Point(0.6, 0.15, 0.10),
    Point(1.0, 0.0, 0.15),
]

path_hermite = extrusion_make_path(30, key_points)
path_spline = extrusion_make_spline(30, key_points)

(
    n_path_hermite=length(path_hermite),
    n_path_spline=length(path_spline),
)

(n_path_hermite = 31, n_path_spline = 31)

Lathe Helpers (latheGen / lathe)

Build axisymmetric reference meshes directly from radial profiles:

z_keys = [0.0, 0.2, 0.6, 1.0]
r_keys = [0.35, 0.25, 0.18, 0.08]

lathe_ref = lathe_refmesh(
    "lathe_profile",
    14,          # around-axis resolution
    40,          # sampling along profile
    z_keys,
    r_keys;
    method=:curve,  # AMAP-like extrema-preserving interpolation
    axis=:x,
    cap_ends=true,
    material=RGB(0.50, 0.38, 0.25),
)

plantviz(lathe_ref)

Procedural RefMeshes and Caching

For reconstruction pipelines, do not rebuild procedural meshes for every node. Keep the same pattern as classic OPF refmeshes: build once, then reuse with node transforms.

Use a small cache keyed by your geometry parameters:

cache = Dict{Any,RefMesh}()
key = (:shaft_r04_l10, 12, 0.4, true)

shaft_ref = get!(cache, key) do
    mesh = extrude_tube_mesh(
        [Point(0.0, 0.0, 0.0), Point(1.0, 0.0, 0.0)];
        n_sides=12,
        radius=0.4,
        cap_ends=true,
    )
    RefMesh("shaft_r04_l10", mesh, RGB(0.55, 0.45, 0.35))
end

# same key => same RefMesh instance reused
shaft_ref_again = cache[key]

shaft_ref === shaft_ref_again

true

Recommended integration rule:

• when many nodes share the same procedural shape parameters: use cached constructors and reuse the RefMesh

• when each node has unique geometry (for example organ-specific measured profile): build one RefMesh per unique parameter set

• keep node placement in Geometry transforms (translation/rotation/scale) as usual

Procedural Node Geometry (Without RefMesh)

If each node has its own geometry parameters, you can assign a procedural geometry object directly to node[:geometry].

ExtrudedTubeGeometry is the first concrete type for that workflow. It is built on demand by the same scene merge/render pipeline used for classic Geometry.

mtg_proc = Node(NodeMTG(:/, :Plant, 1, 1))
stem = Node(mtg_proc, NodeMTG(:/, :Internode, 1, 2))
tube = Node(mtg_proc, NodeMTG(:/, :Internode, 2, 2))

stem[:geometry] = PlantGeom.Geometry(
    ref_mesh=RefMesh(
        "stem_ref",
        GeometryBasics.mesh(GeometryBasics.Cylinder(Point(0.0, 0.0, 0.0), Point(1.0, 0.0, 0.0), 0.06)),
        RGB(0.55, 0.45, 0.35),
    ),
)

tube[:geometry] = ExtrudedTubeGeometry(
    [
        Point(0.0, 0.0, 0.0),
        Point(0.2, 0.03, 0.00),
        Point(0.4, 0.08, 0.01),
        Point(0.7, 0.14, 0.03),
        Point(1.0, 0.18, 0.05),
        Point(1.2, 0.20, 0.06),
    ];
    n_sides=18,
    radius=0.05,
    radii=[1.0, 0.95, 0.88, 0.80, 0.72, 0.65],
    torsion=false,
    cap_ends=true,
    material=RGB(0.35, 0.50, 0.70),
    transformation=PlantGeom.Translation(1.25, 0.0, 0.0),
)

plantviz(mtg_proc)

Cylinder-like Primitive

plantviz(cylinder_refmesh)

Access Properties

(name=cylinder_refmesh.name,
 nvertices=nvertices(cylinder_refmesh),
 nelements=nelements(cylinder_refmesh))

(name = "cylinder_1", nvertices = 32, nelements = 60)

Meshes.jl Interop

PlantGeom's core backend is GeometryBasics, but you can build meshes in Meshes.jl and convert them using the optional extension API:

• to_geometrybasics(mesh::Meshes.SimpleMesh)

• to_meshes(mesh::GeometryBasics.Mesh)

• to_meshes(ref_mesh::RefMesh)

Build a RefMesh from Meshes.jl

using Meshes

mesh_meshes = Meshes.CylinderSurface(
    Meshes.Point(0.0, 0.0, 0.0),
    Meshes.Point(0.0, 0.0, 1.0),
    0.2,
) |> Meshes.discretize |> Meshes.simplexify

mesh_gb = to_geometrybasics(mesh_meshes)
ref_from_meshes = RefMesh("cylinder_from_meshes", mesh_gb, RGB(0.3, 0.5, 0.8))

plantviz(ref_from_meshes)

Convert Back to Meshes.jl

mesh_back = to_meshes(ref_from_meshes)
(
    nverts_meshes = length(collect(Meshes.vertices(mesh_back))),
    nfaces_meshes = length(collect(Meshes.elements(Meshes.topology(mesh_back)))),
)

(nverts_meshes = 152, nfaces_meshes = 300)