Why disappear PhysX when a Modifier is set on Tyflow?

[tyFlow]

Render-only is default to avoid lag/crashing/etc in situations where you're rendering huge numbers of particles as instances.

Consider the following workflow:

Code:

- you setup a flow with 10 million particles
- you now want to render it as instances (rendering as meshes would require too much RAM)
- you drag in a Mesh operator
- since render-only is default, no mesh is created in the viewport and the Mesh operator does nothing when added to the flow until render-time
- you then switch the Mesh operator mode to instances and render, and only a small amount of RAM is consumed

Now consider if render-only was not on by default:

Code:

- you setup a flow with 10 million particles
- you now want to render it as instances (rendering as meshes would require too much RAM)
- you drag in a Mesh operator
- since render-only is *not* on by default, tyFlow attempts to build the mesh of 10 million particles after the Mesh operator is dragged in
- your machine immediately stalls/freezes/crashes due to the RAM requirements for 10 million non-instance particles to be converted into a mesh
- it becomes impossible to add a Mesh operator to a flow with 10 million particles visible in the viewport, without crashing Max immediately

So render-only being default is just a fail-safe for large sims