ArcRotateCamera does not correctlly use upVector

[chadautry]

I don't believe ArcRotateCamera correctly uses the upVector.  Instead of getting into my use case, I've setup some playground demonstrations.

 

Playground 1: This is the default. upVector is Y+. 

Behavior: Move the mouse left, spins clockwise around the Y axis. Move the mouse right, spins counter clockwise. Move the mouse up, pushes the Y+ axis away from the screen, move the mouse down, pulls the Y+ axis towards the screen.

http://www.babylonjs-playground.com/#2K6AJC#2

 

This default works as expected.

 

 

Playground 2: Set the upVector to Z+

Expected Behavior: Move the mouse left and right should spin around the Z axis. Move the mouse up and down should pull the Z axis towards and away from the screen. Unfortunately, that is not the actual behavior.

http://www.babylonjs-playground.com/#2K6AJC#3

 

Thanks

[GameMonetize]

upVector is used by arcRotateCamera (you can also allow upSide down with cam.allowUpsideDown = true)

 

But I think that your problem is that controls are not changed based on upVector

[chadautry]

That could be it. I'm trying browse the code to figure out where to change it to use upVector for the controls. But always hard looking at unfamiliar code.

 

I'd definitely say it is an issue not using upVector in the controls as well as the drawing orientation. Kinda makes upVector pointless for the camera.

 

 

Is there a suggested work around I'm not aware of?

I'm trying to re-write an existing system to use Babylon.js, so changing the scene's co-ordinate system to work with the camera is quite a bit of re-work I don't want to do.

[GameMonetize]

Nope unless adding support for the missing part

 

what do you want to achieve? what is your ultimate goal?

[chadautry]

Re-writting http://chad-autry.github.io/hex-grid-map/#/demo to use Babylon.js

For that framework I have the cartesian co-ordinate system aligned with the screen co-ordinates, so that means the hex grid is flat on the Z=0 

 

Basically the two world co-ordinate systems aren't the same. I'd like to get the nice behavior without re-writting my frameworks co-ordinate system.

[GameMonetize]

ok got it.

 

but the only thing you will have to do is: invert Y and Z 

[chadautry]

Hmm, not sure I'm seeing any "only" to do. It'd be a tedious deal to change in my code.

 

The main difference is what the two frameworks consider up, and the only place I've hit a problem is with the ArcFollowCamera controls.

[GameMonetize]

Perhaps you should check how arcrotatecamera is handling controls:

https://github.com/BabylonJS/Babylon.js/blob/master/src/Cameras/babylon.arcRotateCamera.ts#L391

 

I did not check yet but integrating upVector should not be too complex

[chadautry]

Yeah, I played around with it some. The controls are just changing the alpha and beta angles,

 

I think the point of change is actually https://github.com/BabylonJS/Babylon.js/blob/master/src/Cameras/babylon.arcRotateCamera.ts#L521

 

Tried hacking it up a bit without total understanding and only managed to break it. I need to dig in and comprehend the trig there, I just swapped x --> y --> z --> x is obviously not what needs to happen.

[chadautry]

Ok, by swapping Y and Z  at lines

 

https://github.com/BabylonJS/Babylon.js/blob/master/src/Cameras/babylon.arcRotateCamera.ts#L497

https://github.com/BabylonJS/Babylon.js/blob/master/src/Cameras/babylon.arcRotateCamera.ts#L499

https://github.com/BabylonJS/Babylon.js/blob/master/src/Cameras/babylon.arcRotateCamera.ts#L504

https://github.com/BabylonJS/Babylon.js/blob/master/src/Cameras/babylon.arcRotateCamera.ts#L521

 

I'm getting the behavior I'm wanting.

 

I'll try to get an official pull request going where it uses the upVector to set everything. (It may take quite some time, getting an equivalent re-write of my framework with rotation disabled takes priority for me)

 

 

 

Of further interest: I notice that as I spin the scene with the mouse I get a very pronounced movement of my view point compared to the plane. At first I thought it was all about rounding errors (the target vector is being edited on every rotation increment) But interestingly it only happens with the mouse and not the keyboard. I'll have to investigate further.

[chadautry]

Of course I now notice the lines mentioned above don't change the camera panning with the ctrl key.

[GameMonetize]

Sounds good!

[chadautry]

Wrote in the wrong thread.

Edited December 1, 2015 by chadautry

[GameMonetize]

SOunds really promising man!

[crn]

Has anything happened about this problem? I am currently facing pretty much the same problem and while I could (and will) try the patch by chadautry, it would be really nice to have a real fix for that issue.

[Guest]

Not done yet (looking for volunteers :))

[crn]

I have tried to swap the controllers for keys, (please see: http://www.babylonjs-playground.com/#A83GX#30) but only succeeded partially. While rotating around the z axis (i.e. the new up vector) worked fine, rotation around the other axes lead to some strange effects. In the playground, this can be seen best by rotation around y by pressing the up/down keys. Rotation works fine until you cross the point where the up vector coincides with the view vector, after which the orientation of the y axis changes direction.

While this is somewhat understandable mathematically, this seems to be handled consistently with the default up vector (0, 1, 0), where I can rotate in all directions without any such "discontinuities". I was looking for any special handling for this in the Babylon sources, but was not able to find anything.

Any ideas, hints  to where to look?