[UnityShader]溶解与重现效果

参考链接：http://www.cnblogs.com/Esfog/p/DissolveShader.html

效果图：

从颜色变化来说，有三种，一种是纹理颜色，一种是纹理与黑边的混合颜色，一种是透明(用discard处理，不绘制像素)。还需要一张纹理(任意)，根据它的任意一个通道来控制哪部分先消失。例如上面的效果图用的就是这张纹理的r通道：

如果用的是这张纹理(也就是模型自身的纹理)的r通道，会更加酷：

溶解效果代码如下：

Shader "Esfog/Dissolve" 
{
    Properties 
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _NoiseTex ("NoiseTex (R)",2D) = "white"{}
        _DissolveSpeed ("DissolveSpeed (Second)",Float) = 1
        _EdgeWidth("EdgeWidth",Range(0,0.5)) = 0.1
        _EdgeColor("EdgeColor",Color) =  (1,1,1,1)
        _StartTime("StartTime",Float) = 0
    }
    SubShader 
    {
        Tags { "RenderType"="Opaque" }
        
        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #include "UnityCG.cginc"
             
            uniform sampler2D _MainTex;
            uniform sampler2D _NoiseTex;
            uniform float _DissolveSpeed;
            uniform float _EdgeWidth;
            uniform float4 _EdgeColor;
            uniform float _StartTime;
            
            float4 frag(v2f_img i):COLOR
            {
                float DissolveFactor = saturate((_Time.y - _StartTime) / _DissolveSpeed);
                float noiseValue = tex2D(_NoiseTex,i.uv).r;            
                if(noiseValue <= DissolveFactor)
                {
                    discard;
                }
                
                float4 texColor = tex2D(_MainTex,i.uv);
                float EdgeFactor = saturate((noiseValue - DissolveFactor)/(_EdgeWidth*DissolveFactor));
                float4 BlendColor = texColor * _EdgeColor;
                                
                return lerp(texColor,BlendColor,1 - EdgeFactor);
            }
            
            ENDCG
        }
    } 
    
    FallBack Off
}

重现效果代码如下：

Shader "lyh/Show" 
{
    Properties 
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _NoiseTex ("NoiseTex (R)",2D) = "white"{}
        _DissolveSpeed ("DissolveSpeed (Second)",Float) = 1
        _EdgeWidth("EdgeWidth",Range(0,0.5)) = 0.1
        _EdgeColor("EdgeColor",Color) =  (1,1,1,1)
        _StartTime("StartTime",Float) = 0
    }
    SubShader 
    {
        Tags { "RenderType"="Opaque" }
        
        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #include "UnityCG.cginc"
             
            uniform sampler2D _MainTex;
            uniform sampler2D _NoiseTex;
            uniform float _DissolveSpeed;
            uniform float _EdgeWidth;
            uniform float4 _EdgeColor;
            uniform float _StartTime;

            float4 frag(v2f_img i):COLOR
            {
                float DissolveFactor = saturate((_Time.y - _StartTime) / _DissolveSpeed);
                float noiseValue = tex2D(_NoiseTex,i.uv).r;            
                
                float4 texColor = tex2D(_MainTex,i.uv);
                float EdgeFactor = saturate((noiseValue - DissolveFactor)/(_EdgeWidth*DissolveFactor));
                float4 BlendColor = texColor * _EdgeColor;
                
                clip(1 - EdgeFactor - 0.01);
                return lerp(BlendColor,texColor,1 - EdgeFactor);
            }
            
            ENDCG
        }
    } 
    
    FallBack Off
}

在给出的参考链接中，可以很好地了解到原理，这里就不解释了，而重现效果不过就是溶解效果的反转了。这里需要控制一下时间：

material.SetFloat("_StartTime", Time.realtimeSinceStartup);