For over 13 years we have been wondering, "Nooks and crannies? What the heck does that mean?" and "What the heck is a contour?".

Heck I don't know. But I recently enabled "developer mode" in Starcraft: Battle.net Beta to show everyone what it is. I'm going to post screenshots and make some observations, you decide what it really is.

What is the relation to the nooks and crannies error?
There is a contours limit. When that limit is breached, the nooks and crannies error will occur.









This only shows the third contour, depicted in programming as "contour[2]".






The map is 96x96 and doesn't have many obstructions, yet there are over a thousand contours.







We create a Goliath unit and resize the contour boundry to match our Goliath.


Here's the information I gathered:
The white line is the walkable boundry. The edge of the unit cannot step over this line.
The yellow line is the walkable boundry for the exact center of the unit. The center of the unit (1px) cannot step on or over this line.

We can see from this information that the Goliath should be able to pull a tight squeeze in that cliff, and it does with no room to move up or down.


The green dots plotted along the corners of the yellow line appear to be for unit pathing, but I'm not entirely sure.
The red lines connect the green dots, and that's all there is to it.

End of Briefing

Next: Regions, general pathing, and contour relationship. I've found that contours are restricted to regions, I may post about it if people show interest.

Really nice work, Hein.

It's interesting to notice how even with terrain subtiles providing much finer blocking detail, the engine still tries to simplify it (for larger units).

Though I could swear a goliath might fit into that bottom corner of the raised temple on the upper pic...

Very interesting.
Does every unit have its own contours or why are there multiples? How many types do exist?

What are "regions"?

Atm I would assume that the contours are used for long range pathfinding. That would explain the pathfinding problem with the custom tiny bridge in jungle terrain (Zealot will only use the bridge if you click directly in front of him. Else he will go around it. At least I have that behavior in my mind, but I'm not 100% sure).

But I'm sure that you will find out more about it and I would like to force you to post your research findings.
It's very interesting to see how the Starcraft engine works.

btw, why isn't the whole cliff covered with contours on the second pic?