A birdcage (or bird cage) is a cage designed to house birds as pets. Antique (or antique-style) birdcages are often popular as collectors' items or as household decor but most are not suitable for housing live birds, being too small, or of unsafe materials or construction.ood quality cages designed for pet birds are more suitable. Most parrot cages are made or wrought iron and painted with a non-toxic paint referred to as powder-coating. However, the newest trend in the market is cages made of solid stainless steel.
A viewport is a 2D rectangle that defines the size of the rendering surface onto which a 3D scene is projected.
Then in the layer properties manager simply select the freeze layer in current viewport icon or from the pull down on the layers toolbar select the third icon from the left which looks like the sun half covering a rectangle. It is as simple as that, I am sure there are other ways but that seems to work for me.