Unity implements simple Sketchpad drawing function (notes)

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One 、 Set up the scene

1. Create a plan
2. Turn the camera into an orthogonal camera
3. Create three cube, Attach material
4. Create another cube, Find a palette ,
5. Create a script , Hang on a non inactivated object
6. Create a slider, Put it aside
   

Two 、 Write code

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

public class Draw : MonoBehaviour {
    
    LineRenderer line;
    Material mat;
    public Slider slider;
    int num = 0;// Total painting points 
    Color c;
	// Use this for initialization
	void Start () {
    
        slider.value = 0.1f;
	}
                // Update is called once per frame
    void Update () {
    
        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        RaycastHit hit;
        if (Physics.Raycast(ray,out hit))
        {
    
            if (Input.GetMouseButtonDown(0))
            {
    
                if (c==null)
                {
    
                    return;
                }
                GameObject obj = new GameObject();
                line= obj.AddComponent<LineRenderer>();
                line.material.color= c;
                line.widthMultiplier = slider.value;// Width 
                line.SetPosition(0,hit.point);
                line.SetPosition(1, hit.point);
                num = 0;
            }
            if (Input.GetMouseButton(0))
            {
    
                num++;
                line.positionCount = num;
                line.SetPosition(num - 1, hit.point+Vector3.up*0.2f);

            }
            if (Input.GetMouseButtonDown(1))
            {
    
                StartCoroutine(ChangeColor());
            }
        }
	}
    IEnumerator ChangeColor()
    {
    
        yield return new WaitForEndOfFrame();
        Texture2D texture2D = new Texture2D(Screen.width,Screen.height,TextureFormat.RGB24,true);
        texture2D.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
        texture2D.Apply();
        c = texture2D.GetPixel((int)Input.mousePosition.x, (int)Input.mousePosition.y);
    }
}

3、 ... and 、 effect

Unity Drawing board