add out box

[asukaminato0721]

I am testing plot3d.

but the AspectRatio is strange.

but I think it's acceptable. :). Since the graph is correct.

but missing the box outside makes it hard to "feel the space".

Then I found this may help. https://threejs.org/docs/#api/en/helpers/BoxHelper

But where to add it is a problem, since there may have many objects in a scene.

[paulmasson]

@wuyudi I would suggest adding the BoxHelper outside of all objects in the scene. Here's an example from one of my libraries:

https://github.com/paulmasson/mathcell/blob/master/src/render/threejs-template.js#L63

For this to work you of course need to run through all the input objects and find minimum and maximum extents in all three directions.