Mantra’s Delayed load shader replaces the geometry of whatever object it’s assigned to with geometry loaded from disk at render time. This is very useful when you want to work with light-weight, low-poly geometry for speed in the viewport, but need heavy, high detail geometry at render time.
Delayed load not only means the geometry to instance doesn’t have to be kept in memory, it can also speeds up rendering, since Houdini doesn’t have to write the geometry into the IFD and mantra doesn’t have to read through the geometry as it parses the IFD.
When you're doing point instancing, you can use material parameter overrides on the instanced object to change the file to be loaded by the delayed load shader per-instance. For example, to instance a crowd of soldiers, you could create a few soldier variations in separate geometry files, and randomly select between them per-instance.
The normal method for saving geometry to disk only saves the geometry, not additional render information such as materials. To save both the geometry and material information to an archive, use the Mantra Archive render driver.
See the help for the Delayed Load shader for more information.