What is Underlay in animation?
Underlay is the level that sits below the animation. An overlay/underlay is a non-animated layer of artwork that helps to create depth. An overlay/underlay is a designed separation of more objects from the background than an overlay, as required by the scene’s animation can use the underlay layer for a variety of purposes. For example, when animators undertake line testing, they usually sketch basic animation or develop a matte color.
If a prop does introduce on top of a background, an underlay does use. For instance, in a specific car park outside a building, the car paints underlay for one scene. You might want to provide a clip for comments or approval before continuing your work if you’re undertaking rough animation.
If you have numerous overlapping characters in your project, it may be tough to grasp what is happening because you can see through them. Toon Boom Harmony can automatically build a matte in the Underlay, or even in the Colour Art layer, and fill all the zones inside your characters with it to make them opaque. This method is quick and straightforward, and it allows you to send simple movies.
Underlay planes are similar to overlay planes, except they do display in front of the conventional planes. As a result, text annotation, rubber banding, transitory menus, and motion effects can all benefit from overlays and underlays. In addition, Graphics hardware that supports overlays and underlays can have numerous stacked frame buffer layers, whereas a simple frame buffer only has one. 
Underlay Network – The physical infrastructure on top of which the overlay network does develop is known as the underlay network. It is the underlying network that is in charge of packet delivery across networks.
Underlay
Underlay, also known as underlayment, is a thin layer of cushioning consisting of materials like sponge rubber, foam, felt, or crumb rubber that is spread beneath carpeting to give comfort underfoot, reduce wear on the carpet, and provide sound, moisture, and heat insulation.
Underlay is a term that does used to describe a layer that does place beneath another layer. It also does use to describe a variety of various surface-covering items. For example, the Underlay in vinyl flooring, sometimes known as “linoleum,” is a thin layer of plywood fastened over the structural subfloor to produce a consistent, smooth platform for the sheet vinyl.
