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name: core-data-and-geometry description: "Routes PhiFlow field, geometry, mesh, scene, and data-format workflows." disable-model-invocation: true metadata: disco-role: operating license: MIT

Core Data and Geometry

Use this sub-skill for the core PhiFlow objects that most other workflows build on: fields, grids, geometries, meshes, scenes, and field/scene I/O.

Route here for

• CenteredGrid, StaggeredGrid, PointCloud, Noise, and AngularVelocity
• Box, Sphere, Cuboid, Cylinder, UniformGrid, Mesh, Graph, Heightmap, SDFGrid, and SDF
• Scene.create(), Scene.at(), Scene.list(), Scene.write(), Scene.read(), and scene cleanup helpers
• field.read(), field.write(), field.resample(), field.sample(), and field.reduce_sample()
• Geometry transformations and set operations such as shift, rotate, union, and intersection
• scene / field file formats and legacy compatibility issues

Do not route here

• installation or backend setup -> installation-and-backends
• PDE stepping, fluids, waves, FLIP, or SPH -> physics-and-simulation
• gradients, Jacobians, or inverse design -> optimization-and-learning
• plotting, display, controls, or scalar logs -> visualization-and-ui

Start with these imports

from phi.flow import *
from phi import field, geom, math
from phiml.math import batch, channel, instance, spatial, vec

Most common decisions

1. Grid type: use CenteredGrid for scalar quantities and StaggeredGrid for velocity-like vector fields.
2. Sampling vs resampling: use field.sample() when you need values at a Geometry; use field.resample() or Field.at() when you need compatible field representations.
3. Scene I/O: use Scene.create() for new scenes, Scene.write() to store fields, and Scene.read() to recover them. The scene format stores sim_ folders with *.npz field files.
4. Geometry syntax: prefer keyword constructors such as Box(x=1, y=1) or the explicit slicing form Box['x,y', 0:1, 0:1].
5. Mesh / implicit geometry: use Mesh for unstructured surfaces or volumes, and SDFGrid / SDF when you want implicit shapes.
6. Legacy code: treat Domain as compatibility-only. New workflows should construct grids directly with dictionaries and extrapolation= or boundary= values.

Verified signatures to rely on

• Scene.create(parent_directory, shape=(), name='sim', copy_calling_script=True, **dimensions)
• Scene.write(self, data=dict=None, frame=0, **kw_data)
• Scene.read(self, *names, frame=0, convert_to_backend=True)
• field.read(file, convert_to_backend=True) / field.write(field, file)
• field.resample(value, to, keep_boundary=False, **kwargs)
• field.sample(field, geometry, at='center', boundary=None, **kwargs)
• field.reduce_sample(field, geometry, **kwargs)
• Box(*args, **kwargs) and Box['x,y', ...]
• geom.Box, geom.Sphere, geom.Cylinder, geom.Mesh, geom.Graph, geom.Heightmap, geom.SDFGrid, and geom.SDF

Bundled references and helper

• Detailed workflows: references/workflows.md
• Failure handling: references/troubleshooting.md
• Scene round-trip smoke: scripts/scene_roundtrip.py

From this sub-skill directory, run the smoke helper when you want to verify the field / scene I/O path:

python scripts/scene_roundtrip.py --resolution 16

The helper writes temporary scene data, reads it back through both the scene API and field.read(), and cleans up afterwards.