Combiner Node is useful when your show consists of multiple blocks and each block requires a different group of 3D graphics to be displayed.
You can turn each block on or off individually at any time. Each block can have its own unique in and out animation as well.
The currently inactive blocks poses absolutely no load neither on GPU or CPU. So you can use Combiner Node to preload a number of heavy 3D content at the beginning of the show and then switch between them without delay at any time while keeping a low processor load.
You can find a simple example in [Common]:Tutorials\Misc Samples\Combiner_Node.xcomp.
What you have to do is to attach your different objects groups to different Block X pins of Scene Combiner.
The Active Blocks property determines that which blocks are active currently. It can be the number of one single block or a list of multiple block numbers.
If you attach an ordinary scene hierarchies to the Blocks, the objects will simply appear and disappear when you switch between the blocks.
But if you also need in and out animations for a block you have to add a Combiner Block module as the root of the block. It's basically a Scene Node, but also specifies some extra properties that controls the transition.
You have to specify a Fade In and a Fade Out Time, and if necessary, a Delay Time that results in a time gap between the blocks.
When the block is fading in or fading out the module's Fade output pin will run from 0 to 1 or 1 to 0. It can be used to control the in and out animation of the block.
The simplest usage is when you wire this value into an Opacity of one or more objects:
But you can also use it as a Play Time controller of a Sequencer that implements an appearing motion:
In this case the motion curves have to be placed into the 0-1 interval, and the Sequencer must be in the Playing state. The out animation will be the same as the in animation but played backwards.
If you want a different animation for in and out, you can use the InOut_Sequencer.xcomp utility, and simply use the Active output pin of the Combiner Block which tells if the block is currently active or not.
Within the Sequencer you have to designate the beginning of the out part with a marker.
In this case you have to setup the Fade In and a Fade Out Time of the Combiner Block in accordance with the time of the animation parts in the Sequencer.