Another flag we should consider exposing is FXAA (default: true).  Do we know the performance cost of this?  It could be non-trivial on mobile.

I think we would only FXAA if OIT and FXAA flags are true; however, since not all WebGL implementations, have AA, I could see us exposing a FXAA flag in general.  Perhaps it looks like:
```javascript
scene.orderIndependentTranslucency = true;
scene.fxaaOrderIndependentTranslucency = true;  // used when OIT is used
scene.fxaa = false;  // used always
```

Then we FXAA if
```javascript
scene.fxaa || (scene.orderIndependentTranslucency && scene.fxaaOrderIndependentTranslucency)
```