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Advanced (Physics Level Usage)

Uncheck Load if PhysXLevel 0 (turned off), leave checked Load if PhysXLevel 1 and PhysXLevel 2

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stat flex = Flex CPU stats

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Flex Static Triangle Count

You can see this stat in "Stat Flex GPU"

This number must be kept under 32k at any given point. This can be managed by optimizing the collision flex uses.