前部分知识复习02

一、物体的屏幕UV坐标

float2 ScreenUV = i.pos.xy / _ScreenParams.xy;

二、抓取屏幕图像

GrabPass{" _A "}        //_A为贴图图像名称

      之后需在Pass中声明该贴图才能在Pass中引用此贴图

三、屏幕抓取并制作热效应代码

Shader"unity/HeatDistort 07"
{
	Properties
	{
		_DistortTex("DistortTex",2D)="white"{}
		_DistortUV_X("DistortUV_X",int)=0
		_DistortUV_Y("DistortUV_Y",int)=0
		_Distort("Distort",Range(0,1))=0
	 }

	SubShader
	{
		Tags{"Queue"="Transparent"}
		GrabPass{"_Texture"}

		Pass
		{
			CGPROGRAM

			#pragma vertex vert
			#pragma fragment frag

			#include "UnityCG.cginc"

			sampler2D _Texture;
			sampler2D _DistortTex;
			float4 _DistortTex_ST;
			float _DistortUV_X;
			float _DistortUV_Y;
			float _Distort;

			struct appdate
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD;
			 };

			struct v2f 
			{
				float4 pos : SV_POSITION;
				float2 uv : TEXCOORD;
			 };

			v2f vert(appdate v)
			{
				v2f o;
				o.pos=UnityObjectToClipPos(v.vertex);
				o.uv=TRANSFORM_TEX(v.uv,_DistortTex)+float2(_DistortUV_X,_DistortUV_Y)*_Time.y;
				return o;
			 }

			float4 frag(v2f i):SV_Target
			{
				float4 distort=tex2D(_DistortTex,i.uv);
				float2 ScreenUV=i.pos.xy/_ScreenParams.xy;
				float2 dis=lerp(ScreenUV,distort,_Distort);
				float4 tex=tex2D(_Texture,dis);
				return tex;
			 }

			ENDCG
		 }
	 }
 }