Friday, July 13, 2007

It works again!

After some cursing, hair tearing and generic despair it's working again. Well, it awards deck bonus of 500 points when you clear deck section even when there are droids left in the other section, but that's a minor problem. The most important thing in that is that it now sees section as cleared and knows to turn off the lights,regardless of remaining droids. That means that droids stay put in correct half without teleporting between sections and droids in other sections aren't active at all.

Droids also seems to obey my new "don't start on this waypoint" system, which was evident when I tried entering bridge. I had excluded one waypoint too many, so there wasn't enought starting points for all droids. The game hung when trying to find free waypoint for the last droid. I like nothing more than clear signal when something is wrong :)

New waypoint checking system is a lot faster than the original one. The original check used max. 11 lines every time droid was centered on tile, no matter if there was a waypoint or not. And because of a bug it did it twice per tile! It scanned through Y-sorted list until it found same/higher Y coordinate. As there are only 14 valid Y positions for waypoints it meant that multiple X coordinates needed checking too.

Now every waypoint is marked with magic char, so droids only check for waypoint when they are over one. First check is the the usual droid_centered, and only if that's true game proceeds to find which waypoint data is needed. That test uses binary search to find the correct waypoint among 31 possible ones, so there are max. 5 comparisons.

To cut needed time down even more game calculates simple hash from x & y coordinates and uses that as primary search criteria. Only if that matches (and there are only eight hash collisions total so it doesn't happen often) it needs to test for another byte. And remember - this check will match in the end, it is never done unnecessarily.

Max. time taken is slightly over three raster lines, as seen in the attached picture.

Next beta will be out this weekend.

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