Error:Exception in HostFunction: Wrong object reference. Expected: native object reference at ShadersModule::textureSampler

sableraph · November 20, 2020, 6:17pm

Hello everyone! I’m very happy I found this community and I hope one of you can help me get me out of my current coding pickle

I’m trying to learn the scripting part of Spark AR by following Sohail Mehra’s first tutorial.

However, it is possible something has changed in the API since the tutorial was published because, although I feel like I followed the instructions closely, I’m currently stuck with errors I do not understand how to fix.

Here is the code (error below):

const Materials = require('Materials');
const Shaders = require('Shaders');
const Textures =  require('Textures');

const Time = require('Time');
const Reactive = require('Reactive');

export const Diagnostics = require('Diagnostics');

function print(a)
{
    Diagnostics.log(a);
}

const material0 = Materials.findFirst('material0');
const cameraTexture = Textures.findFirst('cameraTexture0');

function main()
{
    const uvs = Shaders.vertexAttribute({"variableName" : Shaders.vertexAttribute.TEX_COORDS});

    const ct = Reactive.mul(Time.ms,0.001);
    const curve = Reactive.abs(Reactive.sin(ct));
    const color = Shaders.textureSampler(cameraTexture, uvs);
    const modulationColor = Reactive.pack4(curve,0,0,1);
    const finalColor = Reactive.mul(color, modulationColor);

    const textureSlot = Shaders.DefaultMaterialTextures.DIFFUSE;
    material0.setTexture(mix2, {textureSlot: textureSlot});

}

main();

And the error I’m getting:

Error:Exception in HostFunction: Wrong object reference. Expected: native object reference
    at ShadersModule::textureSampler (native)
    at main (file:///7a6d89b6b47ba717bea40ff1cc728f46.js:865:37)
   {
     "line": 24,
     "column": 41,
     "sourceURL": "script.js"
   }

Line 24 is this one:

const color = Shaders.textureSampler(cameraTexture, uvs);

Can anyone point me to what I’m doing wrong? I’d be very grateful.

PS: I’m using Spark AR Studio Version: 102.0.0.27.234

PPS: By the way, if you have any other resources for learning the scripting API (besides the official documentation), that would be amazing!

Thanks!

Tomas_Pietravallo · November 20, 2020, 7:15pm

Yes, indeed the API changed, although you specifically asked for something other than the docs, taking a look might reveal the problem.

The code throws an error on line 24, but it’s pretty hard to tell where that is, I’d recommend using Gists when asking for script related help. But at first glance, I can see that both the method to fetch Textures & Objects are incorrect since the API used in your code was faced out begging on v82 and completely removed on v101; that may be the source of the error

I have a tutorial that covers the new methods, feel free to check it out here

sableraph · November 20, 2020, 7:03pm

Hi Tomas,

Thanks for your answer! I’d love to follow your scripting tutorial but the link seems broken.

Line 24 is this one:

const color = Shaders.textureSampler(cameraTexture, uvs);

PS: You’re totally right about the doc and I did spend a lot of time looking through it What I meant by “besides the official doc” is that I’m looking for additional learning material. The doc is great as a reference but it’s nice to have tutorials that make the learning curve a bit smoother.

Tomas_Pietravallo · November 20, 2020, 7:16pm

Ooops, liked to the wrong repo (that was the draft), I updated the post above but here’s the right link just in case.

Tomas_Pietravallo · November 20, 2020, 7:18pm

There don’t seem to be any problems with line 24 as I suspected, most likely you are getting that error because textureSampler is being fed undefined as a texture. (the uvs are fine)

josh_beckwith · November 20, 2020, 7:32pm

Yep, line 24 is just where the runtime notices the problem. The issue is that findFirst returns a Promise and not a texture, and it complains because it expects a texture.

Check out this section in the tutorial to get an understanding of how to use Promises https://github.com/tomaspietravallo/sparkar-fdccc2020#asyncawait

sableraph · November 20, 2020, 7:45pm

Thanks a lot! I think I’m getting a better understanding of the problem but also realizing that have a lot of learning ahead of me

I’m trying to run the practical example included in the Async/await section of Tomas’ tutorial. First VScode complained that it couldn’t find the names “Textures” and “Materials” so I added the following lines:

const Textures = require('Textures');
const Materials = require('Materials');

Now it is throwing a warning:

Possible Unhandled Promise Rejection: Error: Exception in HostFunction: Wrong object reference. Expected: native object reference

And the texture is all white

sableraph · November 20, 2020, 7:56pm

I tried the same on Sohail Mehra’s tutorial:

gist.github.com

https://gist.github.com/SableRaf/52d31c3636dfa96ca922efff61c91a6f

script.js

const Materials = require('Materials');
const Textures =  require('Textures');
const Shaders = require('Shaders');
const Time = require('Time');
const Reactive = require('Reactive');

async function main()
{
    const material0 = await Materials.findFirst('material0');;
    const cameraTexture = await Textures.findFirst('cameraTexture0');

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I’m getting the same warning:
Possible Unhandled Promise Rejection: Error: Exception in HostFunction: Wrong object reference. Expected: native object reference

And my texture just shows white.

josh_beckwith · November 20, 2020, 8:02pm

One of your Promises is being rejected. You can catch the error and see what it says by adding .catch to it, like this:

const {log} = require('Diagnostics')
//...
const material0 = await Materials.findFirst('material0').catch(err => log(err))

sableraph · November 20, 2020, 8:28pm

Thanks. I tried and my code looks like this:

gist.github.com

https://gist.github.com/SableRaf/9a732ff1a075787c2094b724ac170b6e

script.js

const Materials = require('Materials');
const Textures =  require('Textures');
const Shaders = require('Shaders');
const Time = require('Time');
const Reactive = require('Reactive');

const {log} = require('Diagnostics');

async function main()
{

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It still brings up the same warning.

Possible Unhandled Promise Rejection: Error: Exception in HostFunction: Wrong object reference. Expected: native object reference

I don’t see an error log for the material0 or cameraTexture0 promises.

I added two test logs to isolate the line where the program stops:

log('this prints');
const color = Shaders.textureSampler(cameraTexture0, uvs);
log('this does not print');

josh_beckwith · November 20, 2020, 9:17pm

What happens if you try logging out cameraTexture0?

sableraph · November 20, 2020, 9:47pm

It prints this out:

CameraTexture {
  """
    The `CameraTexture` class represents a texture type that contains image data coming in from system camera, or captured photo/video in case of using the effect with "Media Library".
  """
    }

josh_beckwith · November 23, 2020, 2:25pm

Sorry I’m still unfamiliar with this workflow, but I think you need to get the signal from the texture object.

sableraph · November 21, 2020, 7:51pm

Thanks Josh! I think I’m getting closer but…

gist.github.com

https://gist.github.com/SableRaf/d467afdbbb8302a57f93e1bc44e46525

script.js

const Materials = require('Materials');
const Textures =  require('Textures');
const Shaders = require('Shaders');
const Time = require('Time');
const Reactive = require('Reactive');

const Diagnostics = require("Diagnostics");
const {log} = require('Diagnostics');

async function main()

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I don’t understand what I am supposed to pass to Shaders.vertexAttribute().

The documentation says:

gist.github.com

https://gist.github.com/SableRaf/349ee841a10dfeed335f41e89a4295d0

none

vertexAttribute(config: { variableName: any; }): any

vertexAttribute(config: {variableName: Shaders.VertexAttribute}): GenericVector

Returns a signal for the specified vertex attribute depending on the VertexAttribute used: 

VertexAttribute.POSITION: Point4DSignal 
VertexAttribute.NORMAL: PointSignal 
VertexAttribute.TANGENT: Point4DSignal 
VertexAttribute.TEX_COORDS: Point2DSignal

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So I tried Shaders.vertexAttribute(VertexAttribute.TEX_COORDS)

But I get the following error.

Possible Unhandled Promise Rejection: ReferenceError: Property 'VertexAttribute' doesn't exist

How do you set the attribute to TEX_COORDS?

Tomas_Pietravallo · November 22, 2020, 5:40pm

{variableName: Shaders.VertexAttribute.TEX_COORDS} or {variableName: ‘TEX_COORDS’}, either one should work

sableraph · November 23, 2020, 10:02am

It worked! Thanks Josh and Tomas

Here is the final version for reference:

gist.github.com

https://gist.github.com/SableRaf/a201508a07befa19205732581342ebbe

script.js

const Materials = require('Materials');
const Textures =  require('Textures');
const Shaders = require('Shaders');
const Time = require('Time');
const Reactive = require('Reactive');

// const Diagnostics = require("Diagnostics");
// const {log} = require('Diagnostics');

async function main()

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