How exactly do height (land) and depth (sea) contours work?
Looking at the tools they are just smooth polys with white fills for the land (which lightens the underlying) and dark fills for the sea (which darkens the underlying). They are set to Alpha Transparency, which I'm pretty certain is responsible for the lightening/darkening. Is this the case? If so, what exactly is happening at the pixel level? I've read a bit about alpha channels, but I'm still not grasping it.
Thanks in advance!