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Shape Descriptor

The shape descriptor is a JSON object that consists of three members: kind, dimension and textures.

{
    "kind": "...",
    "dimension": [...],
    "textures": [...]
}

See examples here.

kind

A string value that can be one of following shapes: ground, box, sphere, capsule, cone, cylinder, pyramid, wedge, gear and compound.

dimension

A JSON array that contains shape specific parameters.

kind dimension
ground width, length
box half_width, half_height, half_length
sphere radius
capsule radius, height
cone radius, height
cylinder radius, half_height
pyramid half_width, half_height, half_length
wedge half_width, half_height, half_length, half_top_edge_length
gear radius, half_thickness, num_teeth
compound "child":[{shape descriptor, origin, rotation},...]
  • all numbers are floating point numbers except that num_teeth for gear shape is an integer
  • width(x), height(y), length(z): extend along the designated axis
  • half_width(x), half_height(y), half_length(z): half extend along designated axis on both sides of the shape center
  • half_thickness of the gear shape is along the y axis
  • The wedge shape has a rectangular base parallel to the x-z plane, the top edge is along the z-axis

compound shape

A compound shape allows multiple shapes to be combined to form a more complex shape. Unlike simple shape descriptors, a compound shape descriptor has a JSON array (child) containing objects representing child shapes. Each child shape has a shape descriptot, a 3D vector (origin) for its position relative to the center of the compound shape, and a quaternion (rotation) describing its orientation. A compound shape can be a child shape of another compound shape to form nested commpound shapes.

{
    "kind": "compound",
    "child": [{
        "shape": {<shape descriptor>} or "<name in macros>",
        "origin": [x, y, z],
        "rotation": [x, y, z, r] 
        },
        ...
    ]
}

textures

A JSON array containing one or more texture objects. A texture object has the following form:

{"<texture type>": [<parameters>], "repeat": n}
texture type parameters
horizontal_stripes width, color_1, color_2
vertical_stripes height, color_1, color_2
diagonal_stripes width, height, style, color_1, color_2
checker_board width , height, color_1, color_2
color HTML hex color code or color name
file pathname to an image file (.jpg, .png, etc.)
  • color can be either HTML hex color code ("#DEB887") or color name ("red")
  • pathname to the image file is relative to the JSON file where the texture is defined
  • diagonal_stripes has these styles:
    • 0: top right to bottom left
    • 1: top left to bottom right
    • 2: top center to bottom left and right
    • 3: bottom center to top left and right
  • repeat is an optional integer value that has these meanings:
    • not present: no repeat
    • 0: default texture used for faces with no textures
    • n: repeat this texture n times