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How to return js object to unity

Discussion in 'WebGL' started by alitokur, Sep 17, 2020.

  1. alitokur

    alitokur

    Joined:
    Sep 17, 2020
    Posts:
    3
    I'm using the Google Draco decoder to decode mesh the following.

    Code (JavaScript):
    1. var dracoGeometry;
    2. dracoGeometry = new decoderModule.Mesh();
    3. decodingStatus = decoder.DecodeBufferToMesh(buffer, dracoGeometry);
    when I check the type of the draceGeometrytry:
    Code (JavaScript):
    1. console.log( typeof dracoGeometry);
    I get:
    "object" .

    Now my problem is "how can I return this object to unity". What return type supported in C# to accept js object?
     
    alitokur, Sep 17, 2020
    #1

  2. Marks4

    Marks4

    Joined:
    Feb 25, 2018
    Posts:
    492
    Marks4, Sep 17, 2020
    #2

  3. supron

    supron

    Joined:
    Aug 24, 2013
    Posts:
    67
    HI.
    You can check my library. It's made for Tiny/DOTS but it works with WebGL too. It helps with the transfer of complex objects between C# and JS. It does not support arrays yet, but this function will be implemented within a few days. All you have to know is the structure of your object. The library will do the rest for you.
     
    supron, Sep 17, 2020
    #3

  4. alitokur

    alitokur

    Joined:
    Sep 17, 2020
    Posts:
    3
    @Marks4 As far as I understand these are only solutions valid for string and other primitive data types. but I'm creating a mesh on the js side.
     
    alitokur, Sep 17, 2020
    #4

  5. jukka_j

    jukka_j

    Unity Technologies

    Joined:
    May 4, 2018
    Posts:
    944
    It is not possible to return high-level JavaScript objects back to WebAssembly, since WebAssembly understands only low-level assembly primitives (ints and floats).

    Instead, what people usually do is follow a handle-based approach, where one creates a JavaScript dictionary or an array that holds the high-level JS objects, and then puts the JS object into that dict/array, indexed by a number. Then that number handle is passed back to Unity/WebAssembly side. Then the Unity C# code can point to that object by keeping the handle around.

    When the WebAssembly side wants to perform some kind of action on the object, it will call out to a JavaScript function, and pass that handle there, so that the JavaScript function will know which high-level JS object to pick out from the dict/array.

    For a full example of this in action, see Emscripten repository at https://github.com/emscripten-core/emscripten/blob/master/src/library_webgl.js, which represents GL resources, such as textures and buffers in that fashion.
     
    jukka_j, Oct 6, 2020
    #5