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How to integrate: Script Based Transformation - Best Practise

02 November 2015 13:33 #4724
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
@ Emotional3D
02 November 2015 14:09 #4725
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.
Development Lead | Twitter
02 November 2015 15:57 #4727
You can use main.set_render_callback() for this task.
or main.append_loop_cb()
Blend4Web Team
02 November 2015 16:17 #4728
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.
@ Emotional3D
02 November 2015 16:24 #4729
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.
@ Emotional3D
02 November 2015 18:56 #4737

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.

var m_ctl  = require("controls");
var elapsed = m_ctl.create_elapsed_sensor();
m_ctl.create_sensor_manifold(obj, "MANIFOLD_NAME", m_ctl.CT_CONTINUOUS,
                [elapsed], null, your_callback);
Blend4Web Team
02 November 2015 19:29 #4739
Thank you Ivan, using a sensor in the meantime works like a charm.

@ Emotional3D
02 November 2015 19:44 #4740
Good to know! Thank you for finding bugs!
Blend4Web Team
 
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