TedW posted:Another alternative is to paint the wood flat black. It's amazing how that makes stuff disappear.
Ditto this....
Folks who do theatrical stage sets have for decades used flat black for the very purpose of 'dismissing'. The eye is drawn to color/light. If the mind is to be distracted from an area/object, it's typically painted black. 'In the shadows' is another reason to 'fade to black'...the deeper recesses of a tunnel, for instance.
Ergo, layout track within a tunnel portal?...ballast and create natural or erected bore walls for the first few inches. Then paint/transition everything beyond flat black.
BTW....all of this is a good reason to avoid straight-through tunnel bores on the layout that are positioned so as to invite the viewer to look inside/through....IMHO, of course.
KD
