Alpha/beta not respected on ArcRotateCamera

Bugs
1

https://www.babylonjs-playground.com/#UD9LU6#31

It seems changing target of the camera after setting alpha/beta but BEFORE a frame is rendered makes alpha/beta not be respected.

2

It’s expected the values of alpha/beta will change as the call to setTarget will have them to be recomputed so that the object/vector passed to setTarget is in front of the camera.

3

Yeah, but is it expected that they should be completely reset? It makes not attempt at looking from the direction one has choosen?

Take this one:
https://www.babylonjs-playground.com/#UD9LU6#33
If I:

  1. Start it
  2. Turns it with my mouse
  3. Waits 5 seconds
    … then it changes the target without reseting alpha and beta
4

It is not reset, it is computed according to what you pass to setTarget.

Try to pass a non zero vector, you will see that it changes the display.

5

Look at this.
https://www.babylonjs-playground.com/#UD9LU6#35
I move the target 0.1 units. The alpha/beta should be recomputed to be very nearly the same. But no, my console gives me 0 and 0.01

6

This is a matter of view matrix update. In the same frame you update the camera’s alpha and beta, but the position is calculated during the render process.

Here - https://www.babylonjs-playground.com/#UD9LU6#36 , this will work (if you force view matrix update)

2 Likes
7

Ah, so I wasn’t wrong :slight_smile:
The _getViewMatrix() forces a recompute of the matrix?
Is it legal to use _-methods? Or is it risky business?

8

It is a gray zone? :slight_smile:

If you want to do all three in the same frame, you will have to call this function, or wait a single frame. I wouldn’t call it on each frame actively - this is done through the framework. But calling it from time to time is fine is you really need it.

9

You can call camera.getViewMatrix() instead which is the publicly available function.

1 Like
10

Thanx

11

@Evgeni_Popov @RaananW I want to change beta value of ArcRotateCamera dynamically using Declarative format. But not getting changed.
How should I use getViewMatrix??

<arcRotateCamera
name=“camera”
target={new Vector3(vehicleStyle.targetx, vehicleStyle.targety, vehicleStyle.targetz)}
alpha={cameraPosition?.alpha}
beta={cameraPosition?.beta}
radius={vehicleStyle.radious}
lowerRadiusLimit={vehicleStyle.radious}
upperRadiusLimit={vehicleStyle.radious}
/>

12

there is no need to do anything with the view matrix. changing beta dynamically is fully supported.
I am not sure what the syntax is (i assume JSX), but i would check the value you are passing.

Oh, and it would be great to open a new thread because this one is marked “answered” already :slight_smile:

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