CustomRTRainDrop.shader

Shader "CustomRTRainDrop"{
	Properties{
	    _MainTex ("MainTex", 2D) = "white" {}
        _NoiseTex ("_NoiseTex", 2D) = "white" {}
		_LoopNum ("_LoopNum", Vector) = (1, 1, 1, 1)
	}

	SubShader
	{
	    Tags { "RenderType" = "Transparent" "Queue" = "Transparent" }

	    Pass
	    {
	        ZWrite Off
	        Blend SrcAlpha OneMinusSrcAlpha

	        CGPROGRAM
	        #pragma vertex vert
	        #pragma fragment frag

			#include "UnityCG.cginc"
			#include "UnityCustomRenderTexture.cginc"

			#define HASHSCALE1 .1031
			#define HASHSCALE3 float3(.1031, .1030, .0973)
			#define HASHSCALE4 float4(.1031, .1030, .0973, .1099)
			#define ftime (_Time.y)
			#define PI 3.14159265359
			#define PI2 6.28318530718
			#define Deg2Radius PI/180.
			#define Radius2Deg 180./PI

			float Hash12(float2 p)
			{
				float3 p3  = frac(float3(p.xyx) * HASHSCALE1);
				p3 += dot(p3, p3.yzx + 19.19);
				return frac((p3.x + p3.y) * p3.z);
			}

			sampler2D _MainTex;
			float4 _MainTex_ST;
			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
			};

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

			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				return o;
			}
			float3 ProcessFrag(float2 uv);
			float4 frag(v2f i) : SV_Target{
				float3 uv = ProcessFrag(i.uv); 
				return float4(uv, 1.0);
			}

			fixed2 Rains(fixed2 uv, fixed seed, fixed m) {
				float period = 5;//雨滴在格子中循环的周期
				float2 retVal  = float2(0.0,0.0);
				float aspectRatio = 4.0;//雨滴的宽高比 
				float tileNum = 5;//平铺数量
				float ySpd = 0.1;
				uv.y += ftime * 0.0618;//加点y轴移动 =PI2 /period *0.45*0.55 / tileNum
				uv *= fixed2(tileNum * aspectRatio,tileNum);//栅格化uv
				//加点基于格子的随机值
				fixed idRand = Hash12(floor(uv));
				uv = frac(uv); 
				float2 gridUV = uv;
				uv -=0.5;//(-0.5,0.5)
				//此处uv值范围为(-0.5,0.5)
				//*0.45的原因 是让水滴在格子内游走刚好让上下两个格子之间游走，
				//从而在视觉上格子之间的水滴是可以碰撞的，从而克服格子的空间的分割感
				float t = ftime * PI2 /period;
				t += idRand * PI2;//添加Y随机值
				
				uv.y += sin(t+sin(t+sin(t)*0.55))*0.45;
				uv.y *= aspectRatio;
				//添加x轴随机偏移
				uv.x += (idRand-.5)*.6;

				float r = length(uv);
				r = smoothstep(0.2,0.1,r);
		
				//添加尾迹
				float tailTileNum = 3.0;
				float2 tailUV =uv *  float2(1.0,tailTileNum);
				tailUV.y = frac(tailUV.y) - 0.5;
				tailUV.x *= tailTileNum;
				//在雨滴上面总共有
				float rtail = length(tailUV);
				//尾迹塑形
				rtail *= uv.y * 1.5;
				rtail = smoothstep(0.2,0.1,rtail);
				//切除掉大雨滴下面的部分
				rtail *= smoothstep(0.3,0.5,uv.y);
				retVal = float2(rtail*tailUV+r*uv);
				return retVal;
			}
			
			float3 ProcessFrag(float2 _uv){
				float baseOffset = 0.1;
				float2 uv = _uv;
				uv *= float2(_ScreenParams.x/_ScreenParams.y,1.0);
				float x = (sin(_Time.y*.1)*.5+.5)*.3;
				x =x*x;
				x+= baseOffset;
				float s = sin(x);
				float c = cos(x);
				float2x2 rot = float2x2(c, -s, s, c);
				uv = mul(rot,uv);
				float moveSpd = 0.1;
				float2 rainUV = float2(0.,0.); 
				rainUV += Rains(uv,152.12,moveSpd);
				rainUV += Rains(uv*2.32, 25.23, moveSpd);
				fixed4 finalColor = tex2D(_MainTex, _uv + rainUV*2.);
				return finalColor.xyz;
			} 
	    ENDCG
	}
  }
}