Investigate possible HISMC culling mismatch between tree, vertex and pixel shader

User reports that some foliage/grass instances that are completely culled are actually still being rendered, costing rendering time.

Have a look using Intel GPA or RenderDoc and check pixel shader culling with PerInstanceFadeAmount, vertex shader culling with PerInstanceParams.z in LocalVertexFactory.usf and the instance run generation code is in sync.

Try debug rendering boxes for HISMC tree nodes, and the disable various culling mechanisms to check that culling is operating as it should.