Babylon shows a different result

[fdeng]

Hi Everyone,

I'm a newbie  to Babylon.js, I got a question need someone to help.

When I load a  3D model (eg. obj format model) with Babylon.js, it shows a different result than I expected.

The correct result should be : (The door is on the left side)

 

But with Babylon.js, the model is like below : (the door is on the right side, it seems that all the meshs are rendered opposite direction)

 

Can anybody tell me why?

Is there a parameter that can be set to correct this issue?

 

[sable]

The model might be right handed. You could try:

scene.useRightHandedSystem = true;

 

[fdeng]

@sable Yes, it works after set 

scene.useRightHandedSystem = true;

[brianzinn]

If you have the original model and are exporting it to .OBJ yourself then you can export without needing the scene to be right handed:

• The obj model should be exported with -Z axis forward, and Y axis upward to be compatible with Babylon.js

https://doc.babylonjs.com/how_to/obj

Those options are available in ie: Blender export.

[fdeng]

@sable

Hi,

There is another issue with this right-hand model if the active camera is a FreeCamera.

When the mouse moves in left - right direction, the model moves up - down, while move the mouse up - down, the model moves left - right.

Can anybody tell me how to fix it?

[sable]

Would you be able to make a pg showing that behaviour?

It might though be easier to just export the model as left handed as per @brianzinn above,.

[fdeng]

@sable

@brianzinn

Thanks for you guys' help.

I just found that I set the  rotation of FreeCamera mistake, sorry, please ignore the mouse move issue.

 

As the exporting tool I use has no such exporting option, I can't get a left handed model.

Still, there is something trouble me, it seems that babylon has Y as the up-axis, the building is not standing correctly.

Normally I should see the front, not the bottom of the building.  (You can use ArcRotateCamera to have a look what the building is)

could you please help me on this point.

The PG is below:

https://playground.babylonjs.com/#4QU0BY

[acarvallo]

Hi @fdeng

It looks like many CAD/3D software (mainly for buildings) have the height on the Z axis, while Babylon or other WebGL libraries have Y.

I encountered the same issue and I used a pivot matrix on my mesh to flip the two axis : https://playground.babylonjs.com/#4QU0BY#2

On lines 25-26 you can see the 1's are switched, an untouched matrix would look like this :

1, 0, 0, 0
0, 1, 0, 0
0, 0, 1, 0
0, 0, 0, 1

(You can also put values different than 1, and it will scale on the corresponding axis)

There might be others/better solutions but in my case it seems to work great, and allows to keep original positions.