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Viewport Class

The Viewport manages projection and unprojection of coordinates between world and viewport coordinates.

It provides both direct project/unproject function members as well as projection matrices including view and projection matrices, and can generate their inverses as well to facilitate e.g. lighting calculations in WebGL shaders.

Remarks:

  • The Viewport class perhaps best thought of as the counterpart of the typical Camera class found in most 3D libraries.
  • The main addition is that to support pixel project/unproject functions (in addition to the clipspace projection that Camera classes typically manage), the Viewport is also aware of the viewport extents.
  • Also, it can generate WebGL compatible projection matrices (column-major) - Note that these still need to be converted to typed arrays.

Constructor

Parameters:

  • props (Object) - Viewport properties
    • props.width (Number) - Width of "viewport" or window. Default to 1.
    • props.height (Number) - Height of "viewport" or window. Default to 1.
    • props.viewMatrix (Array[16], optional) - View matrix. Default to identidy matrix.
    • props.projectionMatrix (Array[16], optional) - Projection matrix. Default to identidy matrix.
const viewport = new Viewport({width: 500, height: 500});

Methods

equals

Parameters:

  • viewport (Viewport) - The viewport to compare with.

Returns:

  • true if the given viewport is identical to the current one.
project

Projects latitude, longitude (and altitude) to pixel coordinates in window using viewport projection parameters.

Parameters:

  • coordinates (Array) - [lng, lat, altitude] Passing an altitude is optional.
  • opts (Object)
    • topLeft (Boolean, optional) - Whether projected coords are top left. Default to true.

Returns:

  • A screen coordinates array [x, y] or [x, y, z] if an altitude was given.

Note: By default, returns top-left coordinates for canvas/SVG type render

unproject

Unproject pixel coordinates on screen onto [lng, lat, altitude] on map.

Parameters:

  • pixels (Array) - [x, y, z] Passing a z is optional.
  • opts (Object)
    • topLeft (Boolean, optional) - Whether projected coords are top left. Default to true.

Returns:

  • A map coordinates array [lng, lat] or [lng, lat, altitude] if a z was given.

Note: By default, takes top-left coordinates from JavaScript mouse events.

Source

src/lib/viewports/viewport.js