Wait to execute function in run code till first frame is rendered

Tagged: first render

This topic has 13 replies, 3 voices, and was last updated 3 years, 11 months ago by shantiscript.

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2020-09-02 at 2:46 pm #32334

shantiscript
Customer

Hi,
i am triggering a gltf animation by using a modification of the puzzle code for playing animations from within the runCode() section.
The animations already start playing though before the first render is finished. So half of the animation has already played one the scene actually starts rendering.
How can i make sure that a function is executed just when the first frame has been rendered?

2020-09-02 at 2:58 pm #32335

shantiscript
Customer

Just to add when using the play animation puzzle in the puzzle editor the same thing happens.
The animation starts playing before the first frame is rendered and half of the animation already happened once the first frame renders.
I can’t use autostart (in Blender export) to trigger the animation as there are some other dependencies in javascript in my project, so i need to start the animation by using javascript/puzzle

2020-09-02 at 3:45 pm #32336

Yuri Kovelenov
Staff

Hi,

you can possibly load the animation stopped initially (disable Auto run in Blender), and then start by the play animation puzzle placed in the Main tab.

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2020-09-03 at 5:05 am #32352

GLiFTeK
Customer

You could do what Yuri said but also hide the animated object at scene start, play the animation, use a time puzzle for a little over its animation time length, stop after one play then show it, then it’s “buffered”? For the user to hit play when they want.

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2020-09-03 at 7:36 am #32356
shantiscript
Customer
Hi thanks for the replies!!!
I don’t think you really understand the problem i am running into, so i will try to rephrase.
I disabled auto run in blender for the animation and used the play animation puzzle placed in the main tab as Yuri described.

The problem with that is that the animation starts playing the key frames of the animation before the scene is visible to the user (before the first frame of the actual app is rendered to the screen). Means the animation already starts playing in the background while the loading screen is still indicating the loading. So half of the animation has played once the scene is actually visible to the user.

This is because in my understanding the run() method that is called inside of app.loadScene triggers the render of the app instance after the loadScene callback is fired (once the gltf loader has fetched the gltf into the app instance)
But code thats executed in the puzzles or in run() doesn’t wait for the render function to finish but its executed asynchronously right after the run() function has been called. It doesn’t wait for the first render to be finished and there is no callback or promise to wait for that to happen.
So if the render takes longer to execute all animations triggered with the puzzle on start or in run() will already start running in the background
```
// loaded GLTF 2.0 asset
var url = 'template.gltf';

// construct a new application with simple rotating preloader
var app = new v3d.App('v3d-container', null, new v3d.SimplePreloader({ container: 'v3d-container' }));

// load main scene
app.loadScene(url, function() {
    app.enableControls();
    app.run();
    runCode();
});

function runCode() {
    // place your own code here
}
```
So i need a way to wait for the animation to start until the first render is completed.
2020-09-03 at 9:08 am #32363

Yuri Kovelenov
Staff

Hi,

shantiscript wrote:

So i need a way to wait for the animation to start until the first render is completed.

You can possibly put your function inside a timeout with the 0 seconds period. This will cause it to wait until the next frame is rendered.

Chief 3D Verger | LinkedIn | Twitter

2020-09-03 at 12:29 pm #32374

shantiscript
Customer

Awesome that worked!

2020-09-04 at 3:12 pm #32426

GLiFTeK
Customer

Wow that’s important info.
Glad it worked, and glad I also know now.
High fives all around!

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2020-09-06 at 10:20 am #32462

GLiFTeK
Customer

Yuri Kovelenov wrote:

Hi,

shantiscript wrote:

So i need a way to wait for the animation to start until the first render is completed.

You can possibly put your function inside a timeout with the 0 seconds period. This will cause it to wait until the next frame is rendered.

Yuri did you mean that in re to JavaScript or puzzles? Ie: timeout function vs procedures?

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2020-09-06 at 11:39 am #32465

Yuri Kovelenov
Staff

You can use either the after or the set timer puzzle or the setTimeout JS function. These are basically the same.

Chief 3D Verger | LinkedIn | Twitter

2020-09-06 at 2:14 pm #32467

GLiFTeK
Customer

Yuri Kovelenov wrote:

You can use either the after or the set timer puzzle or the setTimeout JS function. These are basically the same.

Ok that’s what I thought.
Thanks

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2020-11-28 at 8:17 am #36044

shantiscript
Customer

Just an update on this for anyone who might come across this again. There is a better way than using a timeout function to solve this. If the timeout function is too short on a slow device you could still run into running functions before the first frame is actually rendered.
The app instance has a property called frame

https://www.soft8soft.com/docs/api/en/extras/App.html#frame

By checking if the the first app frame has be rendered (for example using an if condition) you can make sure that nothing runs before the first frame has be rendered to the screen

2020-11-29 at 9:12 am #36054

GLiFTeK
Customer

Possibly use a timer puzzle for the first puzzle that executes and say “after frame “0” to have the “first” thing in your puzzles network start?

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2020-11-30 at 6:45 am #36066
shantiscript
Customer
Yeah in the puzzles you would create some function, either a while loop that constantly checks if the first frame has been rendered. Or a interval function that checks if the first frame has been rendered.

In code i created a function that first checks if the first frame has been rendered already and if not it runs a check function at an interval of 200ms. The function returns a promise in booth cases
```
function waitForFirstFrame() {
  return new Promise(resolve => {
    if (appInstance.frame >= 1) {
      resolve()
    } else {
      const waitForFirstFrame = setInterval(() => {
        if (appInstance.frame >= 1) {
          clearInterval(waitForFirstFrame)
          resolve()
        }
      }, 200)
    }
  })
}
```
you can then run or trigger anything that needs to wait till the first frame has ben rendered in the then() block of that function

waitForFirstFrame().then(runAnimations(animations, { frame: 553, speed: 1 }))

in the example runAnimations will wait till the first frame has been rendered and then start an animation
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