How to integrate: Script Based Transformation - Best Practise

Hi @ll,

Is there a best practise(/callback) within the Blend4Web JavaScript API to integrate own JavaScript based scene-transformations calculated by a custom script? (and to be in sync with the scene-animation-loop/update?)
Which callback would be the best? Could you provide any directions or examples?



The flare should be positioned over the cube-frontmost-face-center (on the [faceCenter <-> cameraPos]-axis). For now, the position gets updated in an own loop, with JavaScripts: setInterval, but of course, is lagging behind the original scene.
Which mechanism exist in Blend4Web to hook into the main render loop?

Cheers, Daniel

Hi,

For now, the position gets updated in an own loop, with JavaScripts: setInterval, but of course, is lagging behind the original scene.
Which mechanism exist in Blend4Web to hook into the main render loop?

You can use main.set_render_callback() for this task.

You can use main.set_render_callback() for this task.

or main.append_loop_cb()

Thank you Yuri.

Trying your mentioned set_render_callback() works.
But now I'm seeing the 'lag' isn't coming from the previously out-of sync / rendering in different loops - using the set_render_callback unfortunately produces the same effect as before.
It seems that the camera smoothing/damping is the cause of the (as 'lagging' appearing)-effect.

I'm almost sure that I'm accessing the camera-position the wrong way.
I receive 'a' camera-position, but it appears that this position is the target-camera-position, not the real camera position of that moment, because Blend4Webs standard camera behaviour has a (nice) smooth-damping applied.

The way I access the camera position for now:

camObj = m_scenes.get_object_by_name("Camera");
camPos = m_camera.get_eye(camObj);

or also by trying:

camPos = m_trans.get_translation(camObj);

I would like to keep the camera-smooth/damping active (actually don't know neither how to deactivate it),
what is the right way to access 'real'-current camera position (smooth-damping implied)?

Cheers, Daniel.

Hi Ivan, thank you, too.

I've tried it also with append_loop_cb(), now. But it is the same, the camera-smooth-damping is not implied.

It seems that the camera smoothing/damping is the cause of the (as 'lagging' appearing)-effect.

Yes, this bug is related to camera smoothing. We'll try to fix it by the next release.
It seems that rendering callback isn't suitable at the moment. Instead you can use sensors.

In short, you need to create special elapsed sensor, which allows you to perform different actions every frame, and sensor manifold to register your callback.

Thank you Ivan, using a sensor in the meantime works like a charm.

Good to know! Thank you for finding bugs!