游戏开发中UI提示诱惑特效

    游戏的UI开发中经常会遇到需要制作提示玩家，诱惑玩家注意或点击界面的某个控件的特效。粒子系统是一种解决方案，本文是介绍另外一种解决方案，用倾斜光线扫过控件或标题。效果如下图

思路其实很简单，核心就是对材质的某一层纹理进行uv平移，本例是平移光线纹理的x方向，如下图

本程序运用到U3D提供的纹理位移api material.SetTextureOffset,当光线离开主纹理后，隔200帧重新重右往左移动。程序如下。

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

public class FlashLight : MonoBehaviour
{
    private UITexture tex;
    float m_fOffset = -0.5f;    //x方向的纹理位移
    public int m_fSpeed = 2; //移动速度
    bool m_bStartFlashing = true;    //特效开关

    void Awake()
    {
        tex = GetComponent<UITexture>();
        SetTheTextureOffset(m_fOffset);
        tex.material.SetFloat("_AlphaFactor", 1);
    }
    
    public void SetTheTextureOffset(float offset)
    {
        tex.material.SetTextureOffset("_LightTex", new Vector2(offset, 0));
    }

    public void SetLightFactor(float factor)
    {
        tex.material.SetFloat("_LightFactor", factor);
    }

    void Update()
    {
        if (m_bStartFlashing)
        {
            SetLightFactor(1);
            SetTheTextureOffset(m_fOffset += m_fSpeed * 0.01f);

            if (m_fOffset >= 0.5f)
            {
                m_fOffset = -0.5f;

                SetLightFactor(0);

                m_bStartFlashing = false;

                StartCoroutine(CallBackInFrames(() => { m_bStartFlashing = true; }, 200));
            }
        }
    }

    IEnumerator CallBackInFrames(Action callback, int inFrames)
    {
        int n = 0;
        while (n < inFrames)
        {
            yield return new WaitForFixedUpdate();
            n += 1;
        }
        callback();
    }
}

对应的shader如下。

Shader "Winter/FlashLight" 
{
    Properties 
	{
		 _MainTex ("Base (RGB)", 2D) = "white" { }
		 _AlphaTex("AlphaTex",2D) = "white"{}
		 _LightTex("LightTex",2D) = "white"{}
		 _LightFactor("LightFactor",Float) = 1
		 _AlphaFactor("AlphaFactor",Float) = 1
		 }
    SubShader
	{

		 Tags
		 {
			"Queue" = "Transparent+8"
		 }
         Pass
		 {
			Lighting Off
			ZTest Off
			Blend SrcAlpha OneMinusSrcAlpha
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag

			#include "UnityCG.cginc"

			sampler2D _MainTex;
			sampler2D _LightTex;
			sampler2D _AlphaTex;
			float _LightFactor;
			half4 _Color;

			float _AlphaFactor;
		
			struct v2f 
			{
				float4  pos : SV_POSITION;
				float2  uv : TEXCOORD0;
				float2  uv1 : TEXCOORD1;
			};

			half4 _MainTex_ST;
			half4 _LightTex_ST;
			half4 _AlphaTex_ST;

			v2f vert (appdata_base v)
			{
				v2f o;
				o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
				o.uv = TRANSFORM_TEX (v.texcoord, _MainTex);
				o.uv1 = TRANSFORM_TEX(v.texcoord,_LightTex);
				return o;
			}

			half4 frag (v2f i) : COLOR
			{
				half4 texcol = tex2D (_MainTex, i.uv);
				half4 lightcol = tex2D(_LightTex,i.uv1);

				half4 result = texcol + lightcol* _LightFactor;//这里用纹理叠加效果
				result.a = tex2D(_AlphaTex,i.uv).r * _AlphaFactor;

				return result;
			}
			ENDCG
		 }
    }
} 

场景的GameObject分布如下

运行后得出开头的特效效果。