Shape Visualization
The chunk particles/type_shapes
stores information about shapes
corresponding to particle types. Shape definitions are stored for each type as a
UTF8 encoded JSON string containing keyvalue 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 zerobased. 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]
}