Setting up grid graph questions

Beginner Questions
#1

Hi, I’ve just started to set up the grid graph for my game (A* Pro version, 320 x 320 nodes) and have a few general questions:

  1. The graph gets scanned from code and when it does, I get a log entry such as ‘Process took 1405 ms to complete’. However, on start-up I also get such a message (with a shorter ms value) even though the graph isn’t being scanned then. Is this normal behaviour?

  2. I was able to exclude non-traversable mountain tops in my terrain from the graph by setting the ‘Height testing - Ray length’ value. Is there a similar value I could use to exclude non-traversable bodies of water, e.g. anything below a certain depth? At the moment I’m using an invisible obstacle cube that intersects with my terrain. It works, but seems crude. Is there a better solution? Something like a bounding box maybe for grid graphs?

  3. I have set ‘Connections’ to eight, however it does not work in some cases. I hope the below images illustrate my problem. Is there a setting I might have missed?

astar1
astar11000×620 202 KB

No connection is being made diagonally:

astar2
astar21000×655 247 KB

Thanks for your time and a great asset!

#2
  1. Im unsure why this would be the case, @aron_granberg might be able to answer this
  2. You probably want to have a look at the GraphUpdateScene component for that.
  3. This looks like it might have something to do with your maxStepHeight setting. Im not sure here.
#3

Thank you for your reply.

  1. That seems even more work than just a simple box. I was hoping for a single parameter, like the one used in ‘Ray length’.

  2. There is almost no height differential between both squares, so I dare say the maxStepHeight isn’t going to fix that.

#4

  1. The graph is usually scanned when the game starts. You can control if it is using the A* inspector -> Settings -> Scan On Awake. You can also use cached startup to avoid it (see https://www.arongranberg.com/astar/docs/save-load-graphs.php).
    Normally the first scan takes a lot longer because the C# code needs to be JITed. Therefore subsequent scans normally take significantly less time.

  2. An invisible obstacle cube is usually the best option.
    You can use a custom script which sets walkability based on the y coordinate, but it’s usually simpler to just use a collider.

  3. Diagonal connections require at least one axis aligned connection in the same direction (± 45 degrees). In this case I would recommend a higher resolution of your grid graph, however if necessary I can show you the part of the code you need to modify to change this default behavior.

#5

Thanks Aron, that helps a lot. I prefer to keep the graph resolution 1:1 with my terrain grid, so if you could point me to the part of the code I need to modify to get the diagonal issue sorted, that would be great.

#6

In the GridGenerator.cs script -> CalculateConnections method you need to replace this code

// Loop through axis aligned neighbours (down, right, up, left) or (-Z, +X, +Z, -X)
for (int i = 0; i < 4; i++) {

with

// Loop through all neighbours
for (int i = 0; i < 8; i++) {
#7

Thank you once again, that worked great!

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