PolarGraphGenerator.cs

Shows a simple graph type generating a polar graph.

Version

Tested with version 3.6.7

See Also

Writing Graph Generators

using System.Collections.Generic;
using UnityEngine;
// Include the Pathfinding namespace to gain access to a lot of useful classes
using Pathfinding;
// Required to save the settings
using Pathfinding.Serialization;
using Pathfinding.Util;

// Inherit our new graph from a base graph type
[JsonOptIn]
public class PolarGraph : NavGraph {
    [JsonMember]
    public int circles = 10;
    [JsonMember]
    public int steps = 20;

    [JsonMember]
    public Vector3 center = Vector3.zero;

    [JsonMember]
    public float scale = 2;

    // Here we will store all nodes in the graph
    public PointNode[] nodes;

    GraphTransform transform;

    PointNode CreateNode (Vector3 position) {
        var node = new PointNode(active);

        // Node positions are stored as Int3. We can convert a Vector3 to an Int3 like this
        node.position = (Int3)position;
        return node;
    }

    static Vector3 CalculateNodePosition (int circle, float angle, GraphTransform transform) {
        // Get the direction towards the node from the center
        var pos = new Vector3(Mathf.Sin(angle), 0, Mathf.Cos(angle));

        // Multiply it with the circle number to get the node position in graph space
        pos *= circle;

        // Multiply it with the matrix to get the node position in world space
        pos = transform.Transform(pos);
        return pos;
    }
    public override IEnumerable<Progress> ScanInternal () {
        // Create a 2D array which will contain all nodes
        // This is just a tempoary array to make it easier to reference different nodes
        PointNode[][] circleNodes = new PointNode[circles][];

        // Create a matrix which just moves the nodes to #center
        // and scales their positions by #scale
        // The GraphTransform class has various utility methods for working with it
        transform = new GraphTransform(Matrix4x4.TRS(center, Quaternion.identity, Vector3.one*scale));

        // Place the center node in the center
        circleNodes[0] = new PointNode[] {
            CreateNode(CalculateNodePosition(0, 0, transform))
        };
        // The size of the angle (in radians) each step will use
        float anglesPerStep = (2*Mathf.PI)/steps;

        for (int circle = 1; circle < circles; circle++) {
            circleNodes[circle] = new PointNode[steps];
            for (int step = 0; step < steps; step++) {
                // Get the angle to the node relative to the center
                float angle = step * anglesPerStep;

                Vector3 pos = CalculateNodePosition(circle, angle, transform);
                circleNodes[circle][step] = CreateNode(pos);
            }
        }
        // Now all nodes are created, let's create some connections between them!

        // Iterate through all circles
        // circle 0 is just the center node so we skip that for now
        for (int circle = 1; circle < circles; circle++) {
            for (int step = 0; step < steps; step++) {
                // Get the current node
                PointNode node = circleNodes[circle][step];

                // The nodes here will always have exactly four connections, like a grid, but polar.
                // Except for those in the last circle which will only have three connections
                int numConnections = circle < circles-1 ? 4 : 3;
                var connections = new Connection[numConnections];

                // Get the next clockwise node in the current circle.
                // The last node in each circle should be linked to the first node
                // in the circle which is why we use the modulo operator.
                connections[0].node = circleNodes[circle][(step+1) % steps];

                // Counter clockwise node. Here we check for underflow instead
                connections[1].node = circleNodes[circle][(step-1+steps) % steps];

                // The node in the previous circle (in towards the center)
                if (circle > 1) {
                    connections[2].node = circleNodes[circle-1][step];
                } else {
                    // Create a connection to the middle node, special case
                    connections[2].node = circleNodes[circle-1][0];
                }

                // Are there any more circles outside this one?
                if (numConnections == 4) {
                    // The node in the next circle (out from the center)
                    connections[3].node = circleNodes[circle+1][step];
                }

                for (int q = 0; q < connections.Length; q++) {
                    // Node.position is an Int3, here we get the cost of moving between the two positions
                    connections[q].cost = (uint)(node.position-connections[q].node.position).costMagnitude;
                }

                node.connections = connections;
            }
        }
        // The center node is a special case, so we have to deal with it separately
        PointNode centerNode = circleNodes[0][0];
        centerNode.connections = new Connection[steps];

        // Assign all nodes in the first circle as connections to the center node
        for (int step = 0; step < steps; step++) {
            centerNode.connections[step] = new Connection {
                node = circleNodes[1][step],
                // centerNode.position is an Int3, here we get the cost of moving between the two positions
                cost = (uint)(centerNode.position-circleNodes[1][step].position).costMagnitude
            };
        }
        // Store all nodes in the nodes array
        List<PointNode> allNodes = new List<PointNode>();
        for (int i = 0; i < circleNodes.Length; i++) {
            allNodes.AddRange(circleNodes[i]);
        }
        nodes = allNodes.ToArray();

        // Set all the nodes to be walkable
        for (int i = 0; i < nodes.Length; i++) {
            nodes[i].Walkable = true;
        }
        yield break;
    }

    public override void GetNodes (System.Action<GraphNode> action) {
        if (nodes == null) return;

        for (int i = 0; i < nodes.Length; i++) {
            // Call the delegate
            action(nodes[i]);
        }
    }
}