🔺 Mesh Processing

Genesis provides mesh utilities for loading, simplification, convex decomposition, and collision processing.

Loading Meshes

import genesis as gs

# Load from file
entity = scene.add_entity(gs.morphs.Mesh(file="model.obj"))

# With processing options
entity = scene.add_entity(
    gs.morphs.Mesh(
        file="model.obj",
        scale=0.1,
        convexify=True,
        decimate=True,
        decimate_face_num=500,
    )
)

Decimation

Reduce mesh complexity for collision performance:

gs.morphs.Mesh(
    file="high_poly.obj",
    decimate=True,
    decimate_face_num=500,         # Target face count
    decimate_aggressiveness=2,     # 0-8 scale
)

Aggressiveness levels:

• 0: Lossless

• 2: Preserve features (default)

• 5: Significant reduction

• 8: Maximum reduction

Convex Decomposition

For collision detection, meshes are decomposed into convex parts:

gs.morphs.Mesh(
    file="concave.obj",
    convexify=True,  # Auto-decompose if needed
)

Genesis uses COACD library with configurable options:

gs.options.COACDOptions(
    threshold=0.05,
    max_convex_hull=16,
    resolution=2000,
    preprocess_mode="auto",
)

Collision Processing

Genesis automatically processes collision meshes:

1. Repair: Removes duplicate faces

2. Convexification check: Tests if simple convex hull is sufficient

3. Decomposition: Splits concave meshes into convex parts

4. Decimation: Reduces high-poly meshes (>5000 faces warning)

Tetrahedralization

For FEM/deformable simulation:

entity = scene.add_entity(
    morph=gs.morphs.Mesh(file="model.obj"),
    material=gs.materials.FEM.Elastic(E=1e5, nu=0.4),
)
# Mesh auto-tetrahedralized for FEM

Mesh Properties

mesh = entity.morph.mesh

verts = mesh.verts      # (N, 3) vertices
faces = mesh.faces      # (M, 3) face indices
normals = mesh.normals  # (N, 3) per-vertex normals
uvs = mesh.uvs          # (N, 2) texture coords

is_convex = mesh.is_convex
volume = mesh.volume
area = mesh.area

Particle Sampling

Sample particles from mesh volume:

mesh.particlize(p_size=0.01, sampler="random")

Samplers:

• "random": Random sampling

• "pbs_poisson": Poisson disk sampling

• "pbs_grid": Grid-based sampling

Primitive Meshes

Genesis provides built-in primitives:

gs.morphs.Sphere(radius=0.5)
gs.morphs.Box(size=(1.0, 1.0, 1.0))
gs.morphs.Cylinder(radius=0.3, height=1.0)
gs.morphs.Plane()

Caching

Genesis caches processed meshes for faster loading:

Cache Type	Extension	Purpose
Convex	.cvx	Convex decomposition
Tetrahedral	.tet	FEM tetrahedralization
SDF	.gsd	Signed distance fields
Remesh	.rm	Remeshed versions
Particles	.ptc	Particle sampling

Cache uses SHA256 hash of input parameters for invalidation.

Dependencies

• trimesh: Core mesh operations

• fast_simplification: Decimation

• coacd: Convex decomposition

• pyvista + tetgen: Tetrahedralization