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.. Copyright (c) 2016-2025 The Regents of the University of Michigan
.. Part of GSD, released under the BSD 2-Clause License.
.. _shapes:
Shape Visualization
===================
The chunk :chunk:`particles/type_shapes` stores information about shapes
corresponding to particle types. Shape definitions are stored for each type as a
UTF-8 encoded JSON string containing key-value pairs. The class of a shape is
defined by the ``type`` key. All other keys define properties of that shape.
Keys without a default value are required for a valid shape specification.
Empty (Undefined) Shape
-----------------------
An empty dictionary can be used for undefined shapes. A visualization
application may choose how to interpret this, e.g. by drawing nothing or drawing
spheres.
Example::
{}
Spheres
-------
Type: ``Sphere``
Spheres' dimensionality (2D circles or 3D spheres) can be inferred from the
system box dimensionality.
=============== =============== ====== ==== ======= ======
Key Description Type Size Default Units
=============== =============== ====== ==== ======= ======
diameter Sphere diameter float 1x1 length
=============== =============== ====== ==== ======= ======
Example::
{
"type": "Sphere",
"diameter": 2.0
}
Ellipsoids
----------
Type: ``Ellipsoid``
The ellipsoid class has principal axes a, b, c corresponding to its radii in the
x, y, and z directions.
=============== ===================== ====== ==== ======= ======
Key Description Type Size Default Units
=============== ===================== ====== ==== ======= ======
a Radius in x direction float 1x1 length
b Radius in y direction float 1x1 length
c Radius in z direction float 1x1 length
=============== ===================== ====== ==== ======= ======
Example::
{
"type": "Ellipsoid",
"a": 7.0,
"b": 5.0,
"c": 3.0
}
Polygons
--------
Type: ``Polygon``
A simple polygon with its vertices specified in a counterclockwise order.
Spheropolygons can be represented using this shape type, through the
``rounding_radius`` key.
=============== =============== ===== ==== ======= ======
Key Description Type Size Default Units
=============== =============== ===== ==== ======= ======
rounding_radius Rounding radius float 1x1 0.0 length
vertices Shape vertices float Nx2 length
=============== =============== ===== ==== ======= ======
Example::
{
"type": "Polygon",
"rounding_radius": 0.1,
"vertices": [[-0.5, -0.5], [0.5, -0.5], [0.5, 0.5]]
}
Convex Polyhedra
----------------
Type: ``ConvexPolyhedron``
A convex polyhedron with vertices specifying the convex hull of the shape.
Spheropolyhedra can be represented using this shape type, through the
``rounding_radius`` key.
=============== =============== ===== ==== ======= ======
Key Description Type Size Default Units
=============== =============== ===== ==== ======= ======
rounding_radius Rounding radius float 1x1 0.0 length
vertices Shape vertices float Nx3 length
=============== =============== ===== ==== ======= ======
Example::
{
"type": "ConvexPolyhedron",
"rounding_radius": 0.1,
"vertices": [[0.5, 0.5, 0.5], [0.5, -0.5, -0.5], [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]]
}
General 3D Meshes
-----------------
Type: ``Mesh``
A list of lists of indices are used to specify faces. Faces must contain 3 or
more vertex indices. The vertex indices must be zero-based. Faces must be
defined with a counterclockwise winding order (to produce an "outward" normal).
=============== ================ ====== ==== ======= ======
Key Description Type Size Default Units
=============== ================ ====== ==== ======= ======
vertices Shape vertices float Nx3 length
indices Vertices indices uint32 number
=============== ================ ====== ==== ======= ======
Example::
{
"type": "Mesh",
"vertices": [[0.5, 0.5, 0.5], [0.5, -0.5, -0.5], [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]],
"indices": [[0, 1, 2], [0, 3, 1], [0, 2, 3], [1, 3, 2]]
}
Sphere Unions
-------------
Type: ``SphereUnion``
A collection of spheres, defined by their diameters and centers.
=============== ================ ===== ==== ======= ======
Key Description Type Size Default Units
=============== ================ ===== ==== ======= ======
diameters Sphere diameters float Nx1 length
centers Sphere centers float Nx3 length
=============== ================ ===== ==== ======= ======
Example::
{
"type": "SphereUnion",
"centers": [[0, 0, 1.0], [0, 1.0, 0], [1.0, 0, 0]],
"diameters": [0.5, 0.5, 0.5]
}
|
