terrain variance - what does this do?

I have searched through the forum, but i cant find the answer i want.
What does terrain variance do? I don't understand after checking it with a map i made (you can DL the map frm the attachment).

I made the map so that every 1 second it will tell me the terrain variance of the hero's posistion. But i still don't understand, sometimes it goes up to 16,17 sometimes 0, 4, 8 and so on.

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Another question, if i got a spell "push" (push the targeted unit behind) for example. How do i detect if theres a cliff behind or an obstacles like "Rocks, Trees" so that i can trigger the unit to stop?

I prefer GUI, but if it is needed to use JASS or custom script, i won't mind.
Please help, thanks in advance!

Sry for Double Postin.
But can anyone help me?

Look at this image:



This area is terrained with the same terrain type - But every 128*128 field is not identical. Some places there are stones, dirt, plants - Or the grass just looks different, compared to other fields.

That is terrain variation. Every different variation has an integer id, that you can get by using triggers. You can preview all the different tile variations in the WE:



You can also see the ids of the variations there - Starting from 1. I am pretty sure the jass function counts from 0, and the gui counts from 1.

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To your other question, I would use Jass and GetLocationZ and GetTerrainCliffLevel.

thanks, but i still don't know where that trigger should work in..