In Direct3D Mode, Heimdall offers GPU accelerated video decoding and rendering. But it requires that the PC has Direct3D capable hardware. In some cases this is not available, so Heimdall can also run in less efficient GDI mode.
In hardware accelerated mode, only a small number of Auga instances can be made (depends on the GPU, OS and drivers, typically the limit is 16 instances, but sometimes less). However, a single Auga instance in HW accelerated mode can display many cameras within that instance.
The layout can be set up via the LoadLayoutFromString method, similar to what the Ocularis Client uses.