Unity 3D RTS Style Unit Selection

NSDG | Nov 23, 2019 | 0 Comments
Unity 3D RTS Style Unit Selection
94

In this post I will be showing how to create a RTS (Real-Time Strategy) box style selection in Unity 3D.

So let's begin!

Step 1: Create the necessary scripts

This post features 2 scripts:

SC_Selectable.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SC_Selectable : MonoBehaviour
{
    public Renderer[] renderers; //Assign all child Mesh Renderers

    public Bounds GetObjectBounds()
    {
        Bounds totalBounds = new Bounds();

        for(int i = 0; i < renderers.Length; i++)
        {
            if(totalBounds.center == Vector3.zero)
            {
                totalBounds = renderers[i].bounds;
            }
            else
            {
                totalBounds.Encapsulate(renderers[i].bounds);
            }
        }

        return totalBounds;
    }

    void OnEnable()
    {
        //Add this Object to global list
        if (!SC_SelectionManager.selectables.Contains(this))
        {
            SC_SelectionManager.selectables.Add(this);
        }
    }

    void OnDisable()
    {
        //Remove this Object from global list
        if (SC_SelectionManager.selectables.Contains(this))
        {
            SC_SelectionManager.selectables.Remove(this);
        }
    }
}

SC_SelectionManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SC_SelectionManager : MonoBehaviour
{
    public Texture topLeftBorder;
    public Texture bottomLeftBorder;
    public Texture topRightBorder;
    public Texture bottomRightBorder;

    Texture2D _borderTexture;
    Texture2D borderTexture
    {
        get
        {
            if (_borderTexture == null)
            {
                _borderTexture = new Texture2D(1, 1);
                _borderTexture.SetPixel(0, 0, Color.white);
                _borderTexture.Apply();
            }

            return _borderTexture;
        }
    }

    bool selectionStarted = false;
    Vector3 mousePosition1;

    public static List<SC_Selectable> selectables = new List<SC_Selectable>();
    List<int> selectedObjects = new List<int>();

    // Update is called once per frame
    void Update()
    {
        // Begin selection
        if (Input.GetMouseButtonDown(0))
        {
            selectionStarted = true;
            mousePosition1 = Input.mousePosition;
        }
        // End selection
        if (Input.GetMouseButtonUp(0))
        {
            selectionStarted = false;
        }

        if (selectionStarted)
        {
            // Detect which Objects are inside selection rectangle
            Camera camera = Camera.main;
            selectedObjects.Clear();
            for (int i = 0; i < selectables.Count; i++)
            {
                Bounds viewportBounds = GetViewportBounds(camera, mousePosition1, Input.mousePosition);
                if (viewportBounds.Contains(camera.WorldToViewportPoint(selectables[i].transform.position)))
                {
                    selectedObjects.Add(i);
                }
            }
        }
    }

    void OnGUI()
    {
        if (selectionStarted)
        {
            Rect rect = GetScreenRect(mousePosition1, Input.mousePosition);
            DrawScreenRectBorder(rect, 2, Color.cyan);
        }

        // Draw selection edges
        if(selectedObjects.Count > 0)
        {
            Camera camera = Camera.main;
            for (int i = 0; i < selectedObjects.Count; i++)
            {
                DrawSelectionIndicator(camera, selectables[selectedObjects[i]].GetObjectBounds());
            }
        }
    }

    void DrawScreenRectBorder(Rect rect, float thickness, Color color)
    {
        // Top
        DrawBorderRect(new Rect(rect.xMin, rect.yMin, rect.width, thickness), color);
        // Left
        DrawBorderRect(new Rect(rect.xMin, rect.yMin, thickness, rect.height), color);
        // Right
        DrawBorderRect(new Rect(rect.xMax - thickness, rect.yMin, thickness, rect.height), color);
        // Bottom
        DrawBorderRect(new Rect(rect.xMin, rect.yMax - thickness, rect.width, thickness), color);
    }

    void DrawBorderRect(Rect rect, Color color)
    {
        GUI.color = color;
        GUI.DrawTexture(rect, borderTexture);
        GUI.color = Color.white;
    }

    Rect GetScreenRect(Vector3 screenPosition1, Vector3 screenPosition2)
    {
        // Move origin from bottom left to top left
        screenPosition1.y = Screen.height - screenPosition1.y;
        screenPosition2.y = Screen.height - screenPosition2.y;
        // Calculate corners
        var topLeft = Vector3.Min(screenPosition1, screenPosition2);
        var bottomRight = Vector3.Max(screenPosition1, screenPosition2);
        // Create Rect
        return Rect.MinMaxRect(topLeft.x, topLeft.y, bottomRight.x, bottomRight.y);
    }

    Bounds GetViewportBounds(Camera camera, Vector3 screenPosition1, Vector3 screenPosition2)
    {
        Vector3 v1 = camera.ScreenToViewportPoint(screenPosition1);
        Vector3 v2 = camera.ScreenToViewportPoint(screenPosition2);
        Vector3 min = Vector3.Min(v1, v2);
        Vector3 max = Vector3.Max(v1, v2);
        min.z = camera.nearClipPlane;
        max.z = camera.farClipPlane;

        Bounds bounds = new Bounds();
        bounds.SetMinMax(min, max);
        return bounds;
    }

    void DrawSelectionIndicator(Camera camera, Bounds bounds)
    {
        Vector3 boundPoint1 = bounds.min;
        Vector3 boundPoint2 = bounds.max;
        Vector3 boundPoint3 = new Vector3(boundPoint1.x, boundPoint1.y, boundPoint2.z);
        Vector3 boundPoint4 = new Vector3(boundPoint1.x, boundPoint2.y, boundPoint1.z);
        Vector3 boundPoint5 = new Vector3(boundPoint2.x, boundPoint1.y, boundPoint1.z);
        Vector3 boundPoint6 = new Vector3(boundPoint1.x, boundPoint2.y, boundPoint2.z);
        Vector3 boundPoint7 = new Vector3(boundPoint2.x, boundPoint1.y, boundPoint2.z);
        Vector3 boundPoint8 = new Vector3(boundPoint2.x, boundPoint2.y, boundPoint1.z);

        Vector2[] screenPoints = new Vector2[8];
        screenPoints[0] = camera.WorldToScreenPoint(boundPoint1);
        screenPoints[1] = camera.WorldToScreenPoint(boundPoint2);
        screenPoints[2] = camera.WorldToScreenPoint(boundPoint3);
        screenPoints[3] = camera.WorldToScreenPoint(boundPoint4);
        screenPoints[4] = camera.WorldToScreenPoint(boundPoint5);
        screenPoints[5] = camera.WorldToScreenPoint(boundPoint6);
        screenPoints[6] = camera.WorldToScreenPoint(boundPoint7);
        screenPoints[7] = camera.WorldToScreenPoint(boundPoint8);

        Vector2 topLeftPosition = Vector2.zero;
        Vector2 topRightPosition = Vector2.zero;
        Vector2 bottomLeftPosition = Vector2.zero;
        Vector2 bottomRightPosition = Vector2.zero;

        for (int a = 0; a < screenPoints.Length; a++)
        {
            //Top Left
            if (topLeftPosition.x == 0 || topLeftPosition.x > screenPoints[a].x)
            {
                topLeftPosition.x = screenPoints[a].x;
            }
            if (topLeftPosition.y == 0 || topLeftPosition.y > Screen.height - screenPoints[a].y)
            {
                topLeftPosition.y = Screen.height - screenPoints[a].y;
            }
            //Top Right
            if (topRightPosition.x == 0 || topRightPosition.x < screenPoints[a].x)
            {
                topRightPosition.x = screenPoints[a].x;
            }
            if (topRightPosition.y == 0 || topRightPosition.y > Screen.height - screenPoints[a].y)
            {
                topRightPosition.y = Screen.height - screenPoints[a].y;
            }
            //Bottom Left
            if (bottomLeftPosition.x == 0 || bottomLeftPosition.x > screenPoints[a].x)
            {
                bottomLeftPosition.x = screenPoints[a].x;
            }
            if (bottomLeftPosition.y == 0 || bottomLeftPosition.y < Screen.height - screenPoints[a].y)
            {
                bottomLeftPosition.y = Screen.height - screenPoints[a].y;
            }
            //Bottom Right
            if (bottomRightPosition.x == 0 || bottomRightPosition.x < screenPoints[a].x)
            {
                bottomRightPosition.x = screenPoints[a].x;
            }
            if (bottomRightPosition.y == 0 || bottomRightPosition.y < Screen.height - screenPoints[a].y)
            {
                bottomRightPosition.y = Screen.height - screenPoints[a].y;
            }
        }

        GUI.DrawTexture(new Rect(topLeftPosition.x - 16, topLeftPosition.y - 16, 16, 16), topLeftBorder);
        GUI.DrawTexture(new Rect(topRightPosition.x, topRightPosition.y - 16, 16, 16), topRightBorder);
        GUI.DrawTexture(new Rect(bottomLeftPosition.x - 16, bottomLeftPosition.y, 16, 16), bottomLeftBorder);
        GUI.DrawTexture(new Rect(bottomRightPosition.x, bottomRightPosition.y, 16, 16), bottomRightBorder);
    }
}

Step 2: Setup RTS Selection

  • Create new Game Object and call it _SelectionManager
  • Attach SC_SelectionManager script to _SelectionManager Object
  • Assign textures below to border variables:

  • Drag and drop the Objects you intend to select to Scene (In my case I used models from the Asset Store, check the link below)

RPG/FPS Game Assets for PC/Mobile (Industrial Set v2.0)

  • Attach SC_Selectable script to each model
  • Assign Mesh Renderer (or Mesh Renderers if there is multiple Objects) to Renderers array, this is needed to be able calculate Object bounds.

Now press Play and hold mouse button to begin selection.

Hover over the selectable Objects to select them.