C#•2y ago

❔ How do I get the direction between two points?

Say that you are at position (10, 10) on the map, and your destination is (2, 2). I would like to calculate this and output this: "You need to go northwest." There will be all other directions, too. In my program, my Array2D class is being used to store the 2d array, and (0,0) is at the top-left corner. My function is currently this, assuming I need vectors for it. What do I need to do to achieve this?

        public EDirection GetDirection(int xPos, int yPos, int xDest, int yDest)
        {
            Vector2D pos = new Vector2D(xPos, yPos);
            Vector2D dest = new Vector2D(xDest, yDest);


        }

        public EDirection GetDirection(int xPos, int yPos, int xDest, int yDest)
        {
            Vector2D pos = new Vector2D(xPos, yPos);
            Vector2D dest = new Vector2D(xDest, yDest);


        }

10 Replies

Google•2y ago

Atan2 and a switch statement

triplemochaOP•2y ago

@5YJSA1DG9DFP14705 Since it's a 2d grid, someone recommended just getting the deltas and check for positive/negative. Is that also fine? It seems to be working.

        public EDirection GetDirection(int xPos, int yPos, int xDest, int yDest)
        { 
            int x = xDest - xPos;
            int y = yDest - yPos;

            if ((x == 0) && (y < 0))
                return EDirection.N;
            else if ((x > 0) && (y < 0))
                return EDirection.NE;
            else if ((x > 0) && (y == 0))
                return EDirection.E;
            else if ((x > 0) && (y > 0))
                return EDirection.SE;
            else if ((x == 0) && (y > 0))
                return EDirection.S;
            else if ((x < 0) && (y > 0))
                return EDirection.SW;
            else if ((x < 0) && (y == 0))
                return EDirection.W; 
            else if ((x < 0) && (y < 0))
                return EDirection.NW; 
            else if ((x == 0) && (y == 0))
                return EDirection.Center;
            else 
                return EDirection.Unknown;
        }

        public EDirection GetDirection(int xPos, int yPos, int xDest, int yDest)
        { 
            int x = xDest - xPos;
            int y = yDest - yPos;

            if ((x == 0) && (y < 0))
                return EDirection.N;
            else if ((x > 0) && (y < 0))
                return EDirection.NE;
            else if ((x > 0) && (y == 0))
                return EDirection.E;
            else if ((x > 0) && (y > 0))
                return EDirection.SE;
            else if ((x == 0) && (y > 0))
                return EDirection.S;
            else if ((x < 0) && (y > 0))
                return EDirection.SW;
            else if ((x < 0) && (y == 0))
                return EDirection.W; 
            else if ((x < 0) && (y < 0))
                return EDirection.NW; 
            else if ((x == 0) && (y == 0))
                return EDirection.Center;
            else 
                return EDirection.Unknown;
        }

MODiX•2y ago

JamesK.Polk#2544

REPL Result: Success

var result = GetCardinalDirection(2, 4);
Console.WriteLine(result);
string GetCardinalDirection(int x, int y)
{
    if (x == 0 && y == 0) { return "Origin"; }
    var angle = Math.Atan2(y, x);
    var angleInDegrees = angle * (180 / Math.PI);
    if (angleInDegrees < 0) { angleInDegrees += 360; }

    var directions = new string[] { "North", "Northeast", "East", "Southeast", "South", "Southwest", "West", "Northwest" };
    var index = (int)Math.Round((angleInDegrees % 360) / 45) % 8;
    return directions[index];
}

var result = GetCardinalDirection(2, 4);
Console.WriteLine(result);
string GetCardinalDirection(int x, int y)
{
    if (x == 0 && y == 0) { return "Origin"; }
    var angle = Math.Atan2(y, x);
    var angleInDegrees = angle * (180 / Math.PI);
    if (angleInDegrees < 0) { angleInDegrees += 360; }

    var directions = new string[] { "North", "Northeast", "East", "Southeast", "South", "Southwest", "West", "Northwest" };
    var index = (int)Math.Round((angleInDegrees % 360) / 45) % 8;
    return directions[index];
}

Console Output

Northeast

Northeast

Compile: 716.408ms | Execution: 50.415ms | React with ❌ to remove this embed.

triplemochaOP•2y ago

Any advantage with that example over the less mathy one above?

Google•2y ago

sure.

MODiX•2y ago

JamesK.Polk#2544

REPL Result: Success

var result = GetCardinalDirection(1, 4);
Console.WriteLine(result);
string GetCardinalDirection(int x, int y)
{
    if (x == 0 && y == 0) { return "Origin"; }
    var angle = Math.Atan2(y, x);
    var angleInDegrees = angle * (180 / Math.PI);
    if (angleInDegrees < 0) { angleInDegrees += 360; }

    var directions = new string[] { "North", "Northeast", "East", "Southeast", "South", "Southwest", "West", "Northwest" };
    var index = (int)Math.Round((angleInDegrees % 360) / 45) % 8;
    return directions[index];
}

var result = GetCardinalDirection(1, 4);
Console.WriteLine(result);
string GetCardinalDirection(int x, int y)
{
    if (x == 0 && y == 0) { return "Origin"; }
    var angle = Math.Atan2(y, x);
    var angleInDegrees = angle * (180 / Math.PI);
    if (angleInDegrees < 0) { angleInDegrees += 360; }

    var directions = new string[] { "North", "Northeast", "East", "Southeast", "South", "Southwest", "West", "Northwest" };
    var index = (int)Math.Round((angleInDegrees % 360) / 45) % 8;
    return directions[index];
}

Console Output

East

East

Compile: 685.550ms | Execution: 102.033ms | React with ❌ to remove this embed.

Google•2y ago

the smallest deviation up doesn't apply north to it everything is cordoned into 45 degree arcs.

triplemochaOP•2y ago

I'm confused how to apply the last code example. It only takes in x and y, but not both the position and destination. However, my less math one seems to be working fine.

Google•2y ago

If it works for what you need, that's all that matters!

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ How do I get the direction between two points?