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Massive slowdown at Merge Node

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My scene consists of an asteroid field and a "hero" asteroid together inside a geometry node. Both are slowly revolving around a planet (the planet is in a separate geo node).

I've been rendering Flipbooks to test the revolve/rotation speeds of the asteroids.

If I run a flipbook of just the asteroid field, it takes about 2.5 minutes. A flipbook of just the hero asteroid takes about 1 minute. If I add a merge node so that I can flipbook BOTH the asteroid field and the hero asteroid, it takes well over 20 minutes.

So my question is, what fundamental aspect of the merge node am I not understanding? The only clue I see about something weird is that the merge node indicates a "mis-match of attributes on the inputs" error but I don't think that would cause the slowdown (I'm assuming it's some UV thing). I suppose a better way to build my project would be to break the hero asteroid out into it's own separate geometry node but why would the merge inside the same geo node cause nearly an exponential slowdown? I have 96 GB of RAM so I can't believe it's some hardware limitation. Thank you.


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I think: because each group of your objects in your merge node inputs are too far away from eachother, merging them you will create a huge bounding box in memory, so  Houdini have to handle  a big cluster of memory...

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