Performance of Icons in TrackNode object

[keince]

Is there any way of improving rendering performance of Icons in the TrackNode object? We're seeing a frame rate of 30 (stats handler) with 1000 trackNode objects just displaying the Icon. When we add another Icon to the TrackNode, the frame rate drops to 15 (basically halved). We are using an update callback for our trackNode objects that is pretty involved but I don't think that's the culprit for the marginal performance we're seeing.

It appears that the cull traversal is really working even when the TrackNode objects are all visible. I'm assuming this is because of the AutoTransform being performed in the cull traversal?

When I disable the Icon and use a simple geometry (square) in the TrackNode object, the frame rate improves to around 40 which surprised me.

We have the declutter engine currently disabled since we need to see all the tracks at the same time.

We're using osgEarth 3.1 on a machine using an Intel i7 with 16 processors. Our graphics card is a NVIDIA Quadro T2000/PCIe/SSE2.

Any suggestions for improve rendering performance?