Gaps between Orthophotos and strange lines.

[Colin S]

The first question is of scenery development: Although I have snapped the corners of my draped polygon (quadrangular, no possibility of a stray node causing the gaps) and in WED they appear to be 100% snug against eachother, the polygons seem to have a gap between them.

 

 

The second question is one of rendering: why do these grey lines appear with the terrain hidden by the mountain?