> In fact it works with the provided example but, empirically, it does not on area detail of detailed maps. Crests and valleys will switch.
I don't think that's always the case though: I think it's likely similar to optical illusions: you can technically correctly see it both ways, but it depends on the person's brain and what they're used to as to how their brain sees it.
> That is a consequence of consolidated established style, not a cause.
I didn't say it was a cause, I said that it might lead people to be able to more readily recognise top/left as the lighting direction more readily as "raised" due to being used to computer UIs having top/left being lighter signifying raised elements, and them being more familiar with it that way.
Try it. In my initial experiments as a cartographer, as is normal for learners I did "fix it", and tried "boreal morning or afternoon real light directions": the effect will be wrong, in an actual map. ...Learners "make it the right way" and learn that the """right""" way is wrong.
> more readily
Sure consolidated UIs will contribute in the spiral of circular consolidation of natural ("brain") patterns and conventions, but the "light from top-left" use predates UIs by very many centuries: when we read a document it is more typical to have it lit, not darkened by one's own shadow from a body interposed between sun and document; when we gather around a fire we face it.
I don't think that's always the case though: I think it's likely similar to optical illusions: you can technically correctly see it both ways, but it depends on the person's brain and what they're used to as to how their brain sees it.
> That is a consequence of consolidated established style, not a cause.
I didn't say it was a cause, I said that it might lead people to be able to more readily recognise top/left as the lighting direction more readily as "raised" due to being used to computer UIs having top/left being lighter signifying raised elements, and them being more familiar with it that way.