### David joined Aug 1, 2009

Indie Game Developer (like the movie). I made a couple of games and I usually tweet a lot.

My Blogs

#### A* Pathfinding

For my current project I've been working with A* as a path-finding solution.

Basically it's a way to get from point A to point B.

This is used for AI in games mostly on tiled based games, It's very simple to understand and implement.

As A* traverses the graph, it follows a path of the lowest known cost, keeping a sorted priority queue of alternate path segments along the way. If, at any point, a segment of the path being traversed has a higher cost than another encountered path segment, it abandons the higher-cost path segment and traverses the lower-cost path segment instead. This process continues until the goal is reached.

The major choke point is the heuristic used to calculate which node to take next. I've started by using Manhattan Distance.
Its primary advantage is that it will generally get you to the target faster than most alternatives. Its primary drawback is that in a 8-way pathfinder so it is not guaranteed to give us the shortest possible path.

code:
float cost = 10*(abs(currentX-targetX) + abs(currentY-targetY))

Although it works fast it's not accurate and if I forced for finding the shortest possible it was rather slow for my 80x44 grid (3520 tiles), sometimes taking 3-4 seconds to find a path.

I decided to take another approach and using Diagonal Shortcut, its primary advantage is that, because it is balanced, it is able to fully consider small modifiers like a turning penalty or influence map modifier like having a non walkable tile, a rock, a tree, whatever. It is a bit slower than the Manhattan method, though.

code:
float cost;
float xDistance = abs(currentX-targetX)
float yDistance = abs(currentY-targetY)
if (xDistance > yDistance)
cost = 14*yDistance + 10*(xDistance-yDistance)
else
cost = 14*xDistance + 10*(yDistance-xDistance)

In case you are wondering the 10 and the 14 are to define if it's a diagonal or a horizontal/vertical movement since diagonals take longer to traverse than straight lines of course.
After I'm getting much faster movements.

It's not that Manhattan is worse and you shouldn't use it, it all depends on the application your using.

* On a square grid that allows 4 directions of movement, use Manhattan distance.
* On a square grid that allows 8 directions of movement, use Diagonal distance.

This is a video I've done using Manhattan distance using tile grids generated from a black and white image.

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wow um PortuguÊs por aqui
isto hoje em dia é dificil de encontrar

bem boa sorte para o teu projecto, segundo li, estás quase a acabá.lo.
Fico à espera ;)

cheerz

Creator

Heheh thanks.
Só vi agora aqui o comment. Pensava que o indieDB alertava. É difícil fazer track a isto tudo.
Sim está mesmo quase o jogo. Vamos lá a ver.

yes okay.

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Nice, the other games were really good T.co

1hour ago

Also gonna start sending the USA press codes for Wii U and 3DS, just got them. \o/

1hour ago

That was an fun and different day. Super tired but was worth it. Big thank you to @NintendoPT for everything.

1hour ago

Genius, to reduce shipping damages, a Dutch bike company printed a television on their boxes Theverge.com

9hours ago

RT @LisaHignett: Good lord. It's beautiful! T.co

9hours ago

oh, QoD for 3DS just showed up on USA website with a Sep 29 release date (same as WiiU). Waiting for EU confirmation Nintendo.com

13hours ago

Got an invitation from @NintendoPT to visit their offices later today and have them play a bit of QoD. Will try to take pictures if I can

13hours ago

Morning everyone! This should be an interesting week. 3 days left!

14hours ago

RT @massivegalaxy: Still finishing the city scene, added some 'zx spectrum logo' colors to the car #gamedev #indiedev #pixelart T.co

Sep 25 2016

This is interesting info. Steam speed average downloads speed/traffic around the world Store.steampowered.com T.co

Sep 25 2016

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