[Purist]

Before I get into the rest of the post, I don't think elevation change is overlooked or left out in this section of the forum. Some of us give descriptions of elevation in our track designs to varying degrees. The main thing is, putting it visually into our designs is very difficult and time-consuming. Making those hills and such look more presnetable or realistic adds a further layer of complexity. We do it from time to time, but as far as doing it as a hobby goes, we can't be worrying about all those details all of the time, or it just becomes too much. It ceases to be so much fun, when you overdo it.

Alright, since you prompted it, here are some of my thoughts on the matter.

Elevation Changes
I don't disagree with your take on Tilke, but I'm not convinced that a number of his layouts would be anything spectacular, even with some more pronounced elevation changes. I still think you need a layout that just looks "right" in plan form in order to create a truly great circuit. Now, the right arrangement of hills and valleys is what can turn an alright or good layout into a masterpiece.

The other problem we see with Tilke's efforts is the simple fact that he has a given piece of ground to work with, which may be flat as a pancake, or near to it. With his track outside Istanbul, he had a very rolling terrain to work with, and came up with a rather nice result.

It would be exceedingly difficult to create a wonderful, artificail landscape from scratch, and anyway, the real money in today's F1 circuits goes into the buildings and amenities, not into the track itself. Abu Dhabi is the epitome of this.

I actually had heard of Mas du Clos a while back, when I stumbled onto some thread here, so I am somewhat familiar with that track and its wonderful undulations.

I very much like the old Clermont-Ferrand as well. It was not on the same massive scale as some other public road circuits, but it was still an excellent course. I'm not as much a fan of the truncated layout used there nowadays.

The Nurburgring Nordschleife, well, it needs no further explanation to those who know it. Those who don't just have to see it to believe it.

Getting your elevation change "right" is a very tricky thing. For instance, you may be looking at whether to run more or less straight down a hill, or at doing a series of diving sweepers instead. You might take a more diagonal route up a hill, or attack it head-on with how you position a particular stretch.

Of course, with fantasy tracks, you can make these decisions at will, and so long as your ups and owns can be made to add up, you're fine. I certainly didn't skimp on my written description of the very hilly path carved by my design for Montello Park. I also gave a rolling ground track to one of Yannick's designs a while back.

Probably the biggest thing I can say to try and help others when they look at their designs is that variation is the key. Mix your combinations of up and down. If you can't do it visually, in the written record, differentiate between some steep and some gradual or moderate rises and falls. Having the terrain lend banking or a touch of adverse camber to your turns is always a nice touch.

It's not really about being complex either. Just try to make the elevation fit with the circuit. And you can turn a seemingly simple hillside into varied segments that provide plenty of challenge for an entire lap. Mosport Park basically goes down a hill in a couple stages, and then comes back up that hill.

If you have this gift, it can be an invaluable thing to be able to mentally construct your track in all its sinuous splendour. Being able to "see" the circuit in your mind's eye is the most powerful tool you can have at your disposal. Even if you're on the construction site of a design coming to fruition, you likely can't see the whole track if there are significant hills incorporated into the layout. So, visualizing the scene for yourself on the spot is still extremely useful.

I really can't provide any hard and fast guidelines in this area, because there are so many things that can work when done right. There are just as many ways to get a poor result also, but so much is conditional and contextual that you can't make effective, solid rules with regards to elevation change in your track designs. As long as you don't have the track going over a sheer cliff, or straight into one, your own imagination is the main limiting factor.