Reset the cache of reserved graphics memory used for efficient rendering of Particle Systems.
In order to efficiently write its data into graphics memory, the Particle System uses a pool of pre-allocated vertex buffers. When rendering a large number of particles, this pool will increase in size, and then maintain this size even when rendering fewer particles afterwards.
Maintaining a large pool can make future rendering more efficient, in situations where a large number of particles are being rendered, and the pool is already pre-sized appropriately. However, a large pool uses more memory, so this function allows that memory to be released.
This method is most useful when you know that you have finished rendering a high number of particles, and will not need to render a similar amount in the near future, i.e. when transitioning from a scene containing a large number of particles, to one where fewer particles will be rendered.
Modern graphics APIs, such as DirectX12, Vulkan and Metal, do not use a pre-allocated pool of vertex buffers, because they can operate efficiently without it. This method does nothing on these devices.