using UnityEngine;

public class MagnifyingGlass : PostEffectsBase
{
    //放大的工具
    public Transform tool;
    //是否开始放大
    public bool isStartEnlarge = false;

    // shader
    private Shader myShader;
    //材质 
    private Material mat = null;
    public Material material
    {
        get
        {
            // 检查着色器并创建材质
            mat = CheckShaderAndCreateMaterial(myShader, ref mat);
            return mat;
        }
    }

    // 放大强度
    [Range(-2.0f, 2.0f), Tooltip("放大强度")]
    public float zoomFactor = 0.4f;

    // 放大镜大小
    [Range(0.0f, 0.2f), Tooltip("放大镜大小")]
    public float size = 0.15f;

    // 凸镜边缘强度
    [Range(0.0001f, 0.1f), Tooltip("凸镜边缘强度")]
    public float edgeFactor = 0.05f;

    // 遮罩中心位置
    private Vector2 pos = Vector2.zero;

    void Start()
    {
        //找到对应的Shader文件  
        myShader = shader;
        if (myShader == null)
            myShader = Shader.Find("Custom/MagnifyingGlass");
    }

    // 渲染屏幕
    void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        if (material)
        {
            // 把鼠标坐标传递给Shader
            material.SetVector("_Pos", pos);
            material.SetFloat("_ZoomFactor", zoomFactor);
            material.SetFloat("_EdgeFactor", edgeFactor);
            material.SetFloat("_Size", size);
            // 渲染
            //Graphics.Blit函数使用特定的UnityShader来对当前图像进行处理，再把返回的渲染纹理显示到屏幕上
            Graphics.Blit(source, destination, material);
        }
        else
        {
            Graphics.Blit(source, destination);
        }
    }

    public void Update()
    {
        if (!isStartEnlarge) return;
        //if (tool == null) return;
        //Vector2 mousePos = Camera.main.WorldToScreenPoint(tool.position);
        Vector3 mousePos = Input.mousePosition;
        //将mousePos转化为（0，1）区间
        pos = new Vector2(mousePos.x / Screen.width, mousePos.y / Screen.height);
    }
}