Defining JSON-Based 3D Models

Let's assume, for example, that we have a model object with two arrays: vertices and indices. Say that these arrays contain the information described in the cone example (ch02_06_cone.html), as follows:

function initBuffers() {
  const vertices = [
    1.5, 0, 0,
    -1.5, 1, 0,
    -1.5, 0.809017, 0.587785,
    -1.5, 0.309017, 0.951057,
    -1.5, -0.309017, 0.951057,
    -1.5, -0.809017, 0.587785,
    -1.5, -1, 0,
    -1.5, -0.809017, -0.587785,
    -1.5, -0.309017, -0.951057,
    -1.5, 0.309017, -0.951057,
    -1.5, 0.809017, -0.587785
  ];

  indices = [
    0, 1, 2,
    0, 2, 3,
    0, 3, 4,
    0, 4, 5,
    0, 5, 6,
    0, 6, 7,
    0, 7, 8,
    0, 8, 9,
    0, 9, 10,
    0, 10, 1
  ];

  // ...
}

Following the JSON notation, we would represent these two arrays as an object, as follows:

{
  "vertices": [
    1.5, 0, 0,
    -1.5, 1, 0,
    -1.5, 0.809017, 0.587785,
    -1.5, 0.309017, 0.951057,
    -1.5, -0.309017, 0.951057,
    -1.5, -0.809017, 0.587785,
    -1.5, -1, 0,
    -1.5, -0.809017, -0.587785,
    -1.5, -0.309017, -0.951057,
    -1.5, 0.309017, -0.951057,
    -1.5, 0.809017, -0.587785
  ],
  "indices": [
    0, 1, 2,
    0, 2, 3,
    0, 3, 4,
    0, 4, 5,
    0, 5, 6,
    0, 6, 7,
    0, 7, 8,
    0, 8, 9,
    0, 9, 10,
    0, 10, 1
  ]
}

Based on this example, we can infer the following syntax rules:

• The extent of a JSON object is defined by curly brackets ({}).
• Attributes in a JSON object are separated by commas (,).
• There is no comma after the last attribute.
• Each attribute of a JSON object has two parts: a key and a value.
• The name of an attribute is enclosed by quotation marks ("").
• Each attribute key is separated from its corresponding value with a colon (:).
• Attributes of the array are defined in the same way you would define them in JavaScript.