美术生零基础转行TA中（第7天）

202404010 学习目标：

• 刷课至4.4

学习内容：

4.3 片段的舍弃 Clip

• Clip(x)：如果X<0，则舍弃掉此片段

• 溶解效果

• 修改溶解效果的Tilling Offset

Shader "taecg/Character Unlit"
{
    properties
    {
    [ Header (Base) ]
    [NoScaleOffset] _MainTex ( "MainTex" , 2D ) = "White" { }
    _Color ( "Color",color ) = (0,0,0,0)
    
    [ Space (10) ]
    [ Header (Dissolve) ]
    _DissovlveTex(DissolveTex(R)", 2D ) = "White" { }
    _Clip ( "Clip",Range(0,1)) = 0

    }
    SubShader
    {
        pass
        {
            CGPROGRAM
            #pragma vertex vert
             #pragma fragment frag
             #include "UnityCG/cginc"
             
             spmpler 2D _MainTex;
             fixed4 _color ;
             sampler2D _DissolveTex;float4_DissolveTex_ST;
             fixed _Clip;
             
             struct appdata
             {
                 float4 vertex : POSITION ;
                 float4 uv       : TEXCOORD1;
             } ;
             
             struct v2f
             {
                 float4 pos : SV_POSITION ;
                 float4 uv    : TEXCOORD;
             } ;
             
             v2f vert (appdata v)
             {
                 v2f o ;
                 o.pos = UnityObjectToClipPos ( v.vertex ) ;
                 o.uv.xy = v.uv.xy ;
                 // o.uv.zw = v.uv * DissolveTex_ST.xy+_DissolveTex_ST.zw ; 
                 o.uv.zw = TRANSFORM_TEX( v.uv , _DissolveTex );
                 return 0 ;
             }
             
             fixed4 frag (v2f i) : sv_TARGET
             {                 
                 fixed4 c;
                 fixed4 tex = tex2D( _MainTex, i.uv.xy);
                 c = tex ;
                 c + = _Color;
                 
                 fixed4 dissolveTex = tex2D( _DissolveTex,i.uv.zw);
                 Clip( dissolveTex .r - _Clip );
                 return c;
             }
             
             ENGCG

        }
    
    }

}

4.4 图形计算器

• www.desmos.com
• www.geogebra.org/graphing（用的人比较多）
  

4.4 优化溶解效果

• 希望体现火烧效果

• 溶解边缘有不同颜色变化

• smoothstep ( min, max, x ) 在两个值之间进行平滑过渡 高消耗

  • 如果x比min小，返回0
  • 如果x比max大，返回1
  • 如果x处于范围 [min，max] 中间，则范围0和1之间的平滑值

• saturate （x）线性过渡 低消耗

  • 如果x比o小，返回0
  • 如果x比1大，返回1
  • 如果x处于范围 [0，1] 中间，返回x

  float smoothstep(min,max,x)
  {
  float t=saturate(x-min)/(max-min);
  return t*t*(3-2*t);
  }
  

• 溶解原理：
  

Shader "taecg/Character Unlit"
{
    properties
    {
    [ Header (Base) ]
    [NoScaleOffset] _MainTex ( "MainTex" , 2D ) = "White" { }
    _Color ( "Color",color ) = (0,0,0,0)
    
    [ Space (10) ]
    [ Header (Dissolve) ]
    _DissovlveTex(DissolveTex(R)", 2D ) = "White" { }
    [ NoScaleOffset ]_RampTex ( " RampTex( RGB ) " ,2D ) = "White" { }
    _Clip ( "Clip",Range(0,1)) = 0

    }
    SubShader
    {
        pass
        {
            CGPROGRAM
            #pragma vertex vert
             #pragma fragment frag
             #include "UnityCG/cginc"
             
             spmpler 2D _MainTex;
             fixed4 _color ;
             sampler2D _DissolveTex;float4_DissolveTex_ST ;
             sampler _RampTex ;
             fixed _Clip;
             
             struct appdata
             {
                 float4 vertex : POSITION ;
                 float4 uv       : TEXCOORD1;
             } ;
             
             struct v2f
             {
                 float4 pos : SV_POSITION ;
                 float4 uv    : TEXCOORD;
             } ;
             
             v2f vert (appdata v)
             {
                 v2f o ;
                 o.pos = UnityObjectToClipPos ( v.vertex ) ;
                 o.uv.xy = v.uv.xy ;
                 // o.uv.zw = v.uv * DissolveTex_ST.xy+_DissolveTex_ST.zw ; 
                 o.uv.zw = TRANSFORM_TEX( v.uv , _DissolveTex );
                 return 0 ;
             }
             
             fixed4 frag (v2f i) : sv_TARGET
             {                 
                 fixed4 c;
                 fixed4 tex = tex2D( _MainTex, i.uv.xy);
                 c = tex ;
                 c + = _Color;
                 
                 fixed4 dissolveTex = tex2D( _DissolveTex,i.uv.zw);
                 Clip( dissolveTex .r - _Clip );
                 fixed dissolveValue = saturate (( dissolveTex.r - _Clip ) / ( _Clip + 0.1 - _Clip ))  ;
                 fixed4 rampTex = tex1D(_RampTex , dissolveValue ) ; 
                 c+ = rampTex ; 
                 return c ;
             }
             
             ENGCG

        }
    
    }

}

学习产出：

• 4.3
• 4.4