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热浪扭曲效果的实现,分两部分,一是抓图,二是扭曲扰动.其中难点在于抓图的处理,网上的解决方案有两种,在移动平台都有很多问题,只好自己实现了一种新的方案,效果还不错.
网上方案1. 用GrabPass抓图
GrabPass在有的手机上是不支持的...效率也是问题,所以...
代码可以看看:
- Shader "Luoyinan/Distortion/HeatDistortion"
- {
- Properties
- {
- _NoiseTex ("Noise Texture (RG)", 2D) = "white" {}
- _MainTex ("Alpha (A)", 2D) = "white" {}
- _HeatTime ("Heat Time", range (0,1.5)) = 1
- _HeatForce ("Heat Force", range (0,0.1)) = 0.1
- }
-
- Category
- {
- Tags { "Queue"="Transparent+1" "RenderType"="Transparent" }
-
- Blend SrcAlpha OneMinusSrcAlpha
- AlphaTest Greater .01
- Cull Off
- Lighting Off
- ZWrite Off
-
- SubShader
- {
- GrabPass
- {
- Name "BASE"
- Tags { "LightMode" = "Always" }
- }
-
- Pass
- {
- Name "BASE"
- Tags { "LightMode" = "Always" }
-
- CGPROGRAM
- #pragma vertex vert
- #pragma fragment frag
- #pragma fragmentoption ARB_precision_hint_fastest
- #include "UnityCG.cginc"
-
- struct appdata_t
- {
- float4 vertex : POSITION;
- fixed4 color : COLOR;
- float2 texcoord: TEXCOORD0;
- };
-
- struct v2f
- {
- float4 vertex : POSITION;
- float4 uvgrab : TEXCOORD0;
- float2 uvmain : TEXCOORD1;
- };
-
- float _HeatForce;
- float _HeatTime;
- float4 _MainTex_ST;
- float4 _NoiseTex_ST;
- sampler2D _NoiseTex;
- sampler2D _MainTex;
-
- v2f vert (appdata_t v)
- {
- v2f o;
- o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
- o.uvgrab = ComputeGrabScreenPos(o.vertex);
- o.uvmain = TRANSFORM_TEX( v.texcoord, _MainTex );
- return o;
- }
-
- sampler2D _GrabTexture;
-
- half4 frag( v2f i ) : COLOR
- {
-
- half4 offsetColor1 = tex2D(_NoiseTex, i.uvmain + _Time.xz*_HeatTime);
- half4 offsetColor2 = tex2D(_NoiseTex, i.uvmain - _Time.yx*_HeatTime);
- i.uvgrab.x += ((offsetColor1.r + offsetColor2.r) - 1) * _HeatForce;
- i.uvgrab.y += ((offsetColor1.g + offsetColor2.g) - 1) * _HeatForce;
-
- half4 col = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
-
- col.a = 1.0f;
- half4 tint = tex2D( _MainTex, i.uvmain);
-
- return col*tint;
- }
-
- ENDCG
- }
- }
-
-
-
- SubShader
- {
- Blend DstColor Zero
- Pass
- {
- Name "BASE"
- SetTexture [_MainTex] { combine texture }
- }
- }
- }
- }
网上方案2:用RenderTexture来代替抓图
这种方法很坑爹,把场景再渲染一次?想想就很恐怖
我的方案: 后处理
换种思路,后处理其实就已经有了我们需要抓取的图,我们只需要渲染一个掩码图,就能实现局部的扭曲了,以前做次世代引擎的开发,很多特效都是后处理的实现的,比如人在水里面走水面泛起的涟漪,其实热浪扭曲也可以用类似的方法.
原理:
1.先用后处理实现全屏的扰动
2.用RenderTexture做实时的掩码图.
这样的话,效率开销只在两部分,一是后处理,二是把扭曲面片渲染到掩码图,
优化:
1.掩码图RenderTexture尽可能简单,关掉深度,抗锯齿等,用最简单的格式RenderTextureFormat.RGB565,黑白掩码图,不要alpha通道,掩码面片的shader可以用粒子的add shader
2.不需要扭曲的时候应该关闭掉扭曲用的后处理.不要一直开着.这个实现起来需要对掩码面片的存在有一个计数统计,才知道什么时候能关掉.
3.掩码图的比例一定要和屏幕保持一致,大小可设置为屏幕宽高的1/2或者1/4,
后处理的脚本:
后处理shader:
- Shader "Luoyinan/ImageEffect/HeatDistortion"
- {
- Properties
- {
- _MainTex ("Base (RGB)", 2D) = "white" {}
- _NoiseTex ("Noise Texture (RG)", 2D) = "white" {}
- _MaskTex ("Mask Texture", 2D) = "white" {}
- _HeatTime ("Heat Time", range (0,1.5)) = 1
- _HeatForce ("Heat Force", range (0,0.1)) = 0.1
- }
-
- SubShader
- {
- Pass
- {
- CGPROGRAM
- #pragma vertex vert_img
- #pragma fragment frag
- #pragma fragmentoption ARB_precision_hint_fastest
- #include "UnityCG.cginc"
-
- float _HeatForce;
- float _HeatTime;
-
- uniform sampler2D _MainTex;
- uniform sampler2D _NoiseTex;
- uniform sampler2D _MaskTex;
-
- fixed4 frag(v2f_img i) : COLOR
- {
-
- fixed mask = tex2D(_MaskTex, i.uv).r;
-
-
- half4 offsetColor1 = tex2D(_NoiseTex, i.uv + _Time.xz*_HeatTime);
- half4 offsetColor2 = tex2D(_NoiseTex, i.uv - _Time.yx*_HeatTime);
- i.uv.x += ((offsetColor1.r + offsetColor2.r) - 1) * _HeatForce * mask;
- i.uv.y += ((offsetColor1.g + offsetColor2.g) - 1) * _HeatForce * mask;
-
- fixed4 renderTex = tex2D(_MainTex, i.uv);
-
- return renderTex;
- }
-
- ENDCG
- }
- }
- FallBack off
- }
Unity3D手游开发日记(4) - 适合移动平台的热浪扭曲
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原文地址：http://www.cnblogs.com/czaoth/p/5785632.html
