Bounding box display

[Temechon]

Hello there, 

 

Is there a way to display a model bounding box ?

 

Thank you for your time !

[GameMonetize]

Right now no, you have to create a box and scale it accordingly then display it with wireframe

[Nico]

Hi,

 

If you don't need to draw bounding box in 3D view, you can do it by using a 2D canvas and place it over the 3D view.

You can find an example here : http://jsfiddle.net/nicolas_obre/R9j2z/.

[GameMonetize]

Excellent

[Temechon]

Thanks Nico, it's perfect !

 

Cheers !

[gwenael]

It is what I was looking for, thanks @Nico, unfortunately I found a bug. I modified the jsfiddle to show the bug:

 

http://jsfiddle.net/R9j2z/2/

 

I noticied that the following line gives weird results whereas if you unzoom, the bug doesn't appear anymore and the results are correct:

screenCoordinates = BABYLON.Vector3.TransformCoordinates(screenCoordinates, camera.getProjectionMatrix());

Here are my results:

 

no bug: for i=1 screenCoordinates = (-16.69; -1.59)

no bug: for i=7 screenCoordinates = (-12.74; -4.94)

 

bug: for i=1 screenCoordinates = (15.33; 1.46)

bug: for i=7 screenCoordinates = (21.43; 8.31)

 

For the other i values, results for "bug" and "no bug" do not really change whereas for i=1 and i=7, negative values become positive values.

 

I found in the code the funciton BABYLON.Vector3.Project, I guess we could use it to replace:

var screenCoordinates = BABYLON.Vector3.TransformCoordinates(mesh.getBoundingInfo().boundingBox.vectorsWorld[i], camera.getViewMatrix());screenCoordinates = BABYLON.Vector3.TransformCoordinates(screenCoordinates, camera.getProjectionMatrix());        var objectScreenPosition = new BABYLON.Vector2(screenCoordinates.x * (canvas2D.width / 2) + canvas2D.width / 2, canvas2D.height - (screenCoordinates.y * (canvas2D.height / 2) + canvas2D.height / 2));

but I didn't manage to use it correctly.

[gwenael]

I have updated the jsfiddle to define the getVectorOnScreen function. That's the one to fix...

 

http://jsfiddle.net/R9j2z/3/

 

I tried to fix it by using BABYLON.Vector3.Project without success.

 

http://jsfiddle.net/R9j2z/6/

[gwenael]

Now the maths are correct

 

http://jsfiddle.net/gwenaelhagenmuller/R9j2z/33/

 

These two articles were really helpful http://stackoverflow.com/questions/3329308/perspective-projection-how-do-i-project-points-which-are-behind-camera

http://stackoverflow.com/questions/5666222/3d-line-plane-intersection

 

The issue was due to the fact that some summits of the bounding box can be behind the camera.

Edited January 10, 2014 by gwenael

[Temechon]

Thank you Gwenael for this, it's perfect now

[gwenael]

My pleasure. Nico did the biggest part. I fixed what was needed to be fixed.