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Idaho Airships, Inc.
Idaho Airships, Inc.
Known Participant
February 25, 2019
Question

Parsing a .json File in Expressions

  • February 25, 2019
  • 2 replies
  • 5556 views

Greetings from Boise!

I'm animating a couple of dials in AE using an imported .json file. The file is from a weather station data logger and contains a time, a wind direction, and a wind velocity number at regular intervals recorded every several seconds (among a few other parameters).

What I'd like to do is-for example-is to have the Expression poll the .json file every few seconds and update the dial graphic (rotation) or a text box during rendering.

Does anyone have experience in coding such a thing? Or is anyone interested in the assignment? I am an experienced but out-of-practice .as coder with no time to work on this matter.

Thanks!

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2 replies

Mylenium
Mylenium
Brainiac
February 25, 2019

What I'd like to do is-for example-is to have the Expression poll the .json file every few seconds and update the dial graphic (rotation) or a text box during rendering.

Not possible. All files used for rendering get locked to the AE process and messing around with them while they are being accessed will simply stop the render or crash AE. And given that JSON stuff is still problematic in that even mundane simple files will sometimes not update even while working in AE, this plan is doomed to failure even if other prerequisites and limitations wouldn't apply.

Mylenium

    D
    Dave Merchant
    Brainiac
    February 25, 2019

    Reading the data into the project is easy: The After Effects 2018+ scripting engine has inbuilt support for JSON files as a project item, it automatically parses the contents into a data object. So you simply drop your JSON file into the project panel, then drag it to the New Comp button or into a new layer in an existing comp. Twirl open the layer and you'll see the data arranged as a tree. Here I added a text layer and pick-whipped the Source Text parameter to the "id" data object:

    The JSON file just says:

    {"menu": {
    "id":"file",
    "value":"whatever",
    "popup": 2
    }}

    Of course if the file on disc changes, AE doesn't notice. You can right-click the JSON file in the project panel and "reload footage", or use scripted Scheduled Tasks to force the reload every few seconds, but none of that helps make sense of your statement

    ...to have the Expression poll the .json file every few seconds and update  the dial graphic (rotation) or a text box during rendering.

    After Effects isn't a live-streaming platform. YOU CANNOT CHANGE STUFF DURING A RENDER.

      Idaho Airships, Inc.
      Idaho Airships, Inc.Author
      Known Participant
      February 26, 2019

      Thank you both for answering; I think I did a poor job of describing the matter, though.

      I don't intend to live stream.

      What I'm doing is collecting time lapse thermal video of structures as the sun moves across the sky. During that time lapse collection I also data log the microclimate around the structure using small, certified weather stations.

      Back in the office I'll import the stills into PP and render the video. In AE I need to import the .json (converted from its native .xml) and display the vector dials over the video in such a way that as the Comp renders the weather dials updates indicating the weather parameters as the solar influences change.

      No worries; I can certainly do this AN as I'm very comfortable with AS3 (and can use Greensock to make things a bit more interesting, visually), but it would be quite an elegant thing to do it in AE, especially since I know several folks who need the same functionality and would be happy to buy it. My problem is getting to it; just too busy...

      D
      Dave Merchant
      Brainiac
      February 27, 2019

      If your JSON file is a pre-written array of data objects, then you import it and use an expression to get the value into whatever is controlling your graphics.

      Unless you format your JSON into the special mograf format there's no automatic connection from an array of data objects to composition time, so you have to do it by hand. Suppose your imported JSON is just an array with one value per second, like this:

      [

      { "mything": 0.01 },

      { "mything": 0.03 },

      { "mything": 0.41 },

      { "mything": 0.12 }

      ]

      then you could put this in a text layer's Source text expression:

      var timeval = Math.round(time);

      footage("demo.json").dataValue([timeval,0]);

      Unless we see your data file format and understand what it's going to drive on screen, that's as much help as we can provide.

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