I have a large ground (grid 120x120) on which I grew a meadow, e.g. 6 packed primitives copied to 8 million points. To make this more? efficient, I fractured the ground into 20 fragments and read each fragment as a packed disk primitive - to avoid loading when the camera does not see it.

When I render an individual fragment (~400K points), mantra takes about 1.4GB of memory. When I render all of them together (~8M points), it's around ~30GB. According to SideFX, each instance of a packed primitive should take only 400 bytes. That would translate to 150M (400K points) or 3GB (8M points) respectively.

Can somebody here help me understand what's going on? Perhaps, I misunderstand how this is supposed to work.

If you are interested, here is the scene file: https://drive.google.com/file/d/0B3SRWSd2MwvPVWNqNlZxazlPN0U/view?usp=sharing [drive.google.com] (Warning, that's about 600MB)

Ps: The grass comes from: http://blog.schdbr.de/houdini-grass/ [blog.schdbr.de]