shapes.rst

Shape Visualization

The 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 b c	Radius in x direction Radius in y direction Radius in z direction	float float float	1x1 1x1 1x1		length length 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 vertices	Rounding radius Shape vertices	float float	1x1 Nx2	0.0	length 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 vertices	Rounding radius Shape vertices	float float	1x1 Nx3	0.0	length 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 indices	Shape vertices Vertices indices	float uint32	Nx3		length 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 centers	Sphere diameters Sphere centers	float float	Nx1 Nx3		length length

Example:

{
    "type": "SphereUnion",
    "centers": [[0, 0, 1.0], [0, 1.0, 0], [1.0, 0, 0]],
    "diameters": [0.5, 0.5, 0.5]
}