[UGUI]UI特效裁剪

参考链接：

https://blog.csdn.net/bn0305/article/details/78058076

https://www.xuanyusong.com/archives/3518

https://blog.csdn.net/wangjiangrong/article/details/79483257

Mask组件的裁剪效果，只对其下的UI元素生效，且在绘制完其下的UI元素后，所在区域的模板缓冲值会恢复为0

要想UI特效也被裁剪，可以计算scrollview四个点在世界坐标的位置，然后在粒子的shader中进行判断，如果在范围内则显示

一.shader

留意标记为add的部分

Shader "Custom/Particles/AlphaBlendedMask" {
    Properties 
    {
        _MainTex ("Particle Texture", 2D) = "white" {}

        //----------------------------------------add--------------------------------
        _MinX("MinX", Float) = 0
        _MinY("MinY", Float) = 0
        _MaxX("MaxX", Float) = 0
        _MaxY("MaxY", Float) = 0
        //----------------------------------------add--------------------------------
    }

    SubShader 
    {
        Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "PreviewType"="Plane" }
        Blend SrcAlpha OneMinusSrcAlpha
        Cull Off Lighting Off ZWrite Off Fog { Color (0,0,0,0) }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            //----------------------------------------add--------------------------------
            float _MinX;
            float _MinY;
            float _MaxX;
            float _MaxY;
            //----------------------------------------add--------------------------------

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float2 uv : TEXCOORD0;

                //----------------------------------------add--------------------------------
                float2 worldPos : TEXCOORD1;
                //----------------------------------------add--------------------------------
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);

                //----------------------------------------add--------------------------------
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xy;
                //----------------------------------------add--------------------------------

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);

                //----------------------------------------add--------------------------------
                float posX = i.worldPos.x;
                float posY = i.worldPos.y;
                fixed result = step(_MinX, posX) * step(posX, _MaxX) * step(_MinY, posY) * step(posY, _MaxY);
                return result * col + (1 - result) * fixed4(0, 0, 0, 0);
                //----------------------------------------add--------------------------------

                //return col;
            }
            ENDCG
        }
    }
}

二.c#

计算scrollview四个点在世界坐标的位置

using UnityEngine;

public class UIHelper : CSharpSingletion<UIHelper>
{
    //顺时针
    //1  2
    //0  3
    public Vector4 GetWorldCorners(GameObject go)
    {
        RectTransform rectTransform = go.GetComponent<RectTransform>();
        Vector3[] corners = new Vector3[4];
        rectTransform.GetWorldCorners(corners);
        float minX = corners[0].x;
        float minY = corners[0].y;
        float maxX = corners[2].x;
        float maxY = corners[2].y;
        return new Vector4(minX, minY, maxX, maxY);
    }
}

设置材质

using UnityEngine;

public class UIEffect : MonoBehaviour
{
    Renderer[] renderers;
    MaterialPropertyBlock materialPropertyBlock;

    void Start()
    {
        renderers = gameObject.GetComponentsInChildren<Renderer>();
        materialPropertyBlock = new MaterialPropertyBlock();
    }

    public void SetMask(float minX, float minY, float maxX, float maxY)
    {
        for (int i = 0; i < renderers.Length; i++)
        {
            Renderer renderer = renderers[i];
            materialPropertyBlock.Clear();
            renderer.GetPropertyBlock(materialPropertyBlock);
            materialPropertyBlock.SetFloat("_MinX", minX);
            materialPropertyBlock.SetFloat("_MinY", minY);
            materialPropertyBlock.SetFloat("_MaxX", maxX);
            materialPropertyBlock.SetFloat("_MaxY", maxY);
            renderer.SetPropertyBlock(materialPropertyBlock);
        }
    }
}

效果如下：