The scene descriptor is a JSON file that contains information about the camera, the player and things that you can build and place in the scene called rigid bodies. The scene descriptor recognizes these members to create the scene: camera, player, macros, imports and scene. Other members of the scene descriptor are ignored and can be used as annotations.
A rigid body represents a real-world object that is being simulated in software using physics and mathematics and visualized by the computer's graphics system and the software called OpenGL. A rigid body comprises a simple or compound shape, a 3D vector for position, a quaternion for orientation, and mass of the object.
A 3D vector (x, y, z) is represented as a JSON array of three floating numbers [x, y, z]. For example, (1, 0, 0) is a unit vector whose length is 1 on the x-axis.
A quaternion consists of a 3D vector (axis for rotation) and a scalar (angle in degrees for rotation). It is represented as a JSON array of four (4) floating point numbers [x, y, z, angle]. For example [0, 1, 0, 90] represents a 90 degree (counterclock-wise) rotation about the +y axis.
A JSON object that has three members: eye, target and follow.
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eye is a 3D vector describing the camera's position. If the camera follows the player this vector is in the player's local frame otherwise world frame. This is a required member.
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target is a 3D vector representing where the camera is looking at and uses the same reference frame as the eye. This is an optional member. If missing, the camera will look in +z direction if not following the player or at the player vehicle when following.
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follow is a boolean value. If it is true AND a player is present, the camera follows the player vehicle. This is an optional member. The default is false when it is missing.
Example:
"camera": {
"eye": [10, 5, 10],
"target": [0, 0, 0],
"follow": false
}A JSON object that describes the player vehicle. It recognizes two members vehicle and origin. Both members are required.
- vehicle is a string value. It can be either tank or V150.
- origin is a 3D vector describing the player vehicle's position in world frame.
Example:
"player": {
"vehicle": "tank",
"origin": [0, 1.5, 30]
}A JSON object that contains one or more named shape descriptors that can be referened elsewhere in the file.
A JSON array that contains pathnames to other JSON files whose macros will be imported and added to the current macros to extend the available shape descriptors that can be referenced. The pathnames are JSON string values that are relative to the current JSON file.
Example:
"imports": ["objects/building.json", "docs/examples.json"]The scene descriptor is a JSON array that contains one or more rigid body descriptors. A rigid body descriptor is a JSON object that has these members: shape, origin, rotation, and mass.
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shape is either a shape descriptor or a string value that is the name of a shape descriptor in macros.
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origin is a 3D vector describing the rigid body's position in world frame.
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rotation is a quaternion describing the orientation of the rigid body in world frame. This member is optional. If missing, no rotation is applied to the rigid body.
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mass is a JSON floating point number. It is optional. If mass is missing or has a value of 0, the rigid body is static. A static rigid body cannot move.
Example of a rigid body descriptor:
{
"shape": "axes",
"origin": [0, 0, 0],
"rotation": [0, 1, 0, 0],
"mass": 0
}A json file contains one object at the very top level (root). An object is enclosed by { } and contains one or more members separated by a comma (,). Members are in the form of name:value where name is a string enclosed by " ", and value can be a number, a string, a boolean, another object or an ordered array of values enclosed by [ ]. Order of members is not important; however names have to be unique within the same object.
Example of a JSON object:
{
"name": "value",
"array": [1.0, 2, "car", true, {"color":"green"}, null],
"object": {"fruit":"orange"}
}Some useful links: