Toony Colors Pro 2项目分析——身体其他部位shader

分析目标：Toony Colors Pro 2/Examples/Cat Demo/UnityChan/Style 1
项目地址：https://gitee.com/yichichunshui/ToonyColors.git

首先是surf函数：

void surf(Input IN, inout SurfaceOutputCustom o)
{
	fixed4 mainTex = tex2D(_MainTex, IN.UV_MAINTEX);

	//Shadow Color Texture
	fixed4 shadowTex = tex2D(_STexture, IN.UV_MAINTEX);
	o.ShadowColorTex = shadowTex.rgb;
	o.Albedo = mainTex.rgb * _Color.rgb;
	o.Alpha = mainTex.a * _Color.a;

	//Normal map
	half4 normalMap = tex2D(_BumpMap, IN.uv_BumpMap.xy);
	o.Normal = UnpackScaleNormal(normalMap, _BumpScale);
	o.DiffTintMask = mainTex.a;

	//Rim
	float3 viewDir = normalize(IN.viewDir);
	half rim = 1.0f - saturate( dot(viewDir, o.Normal) );
	rim = smoothstep(_RimMin, _RimMax, rim);
	o.Rim = rim;

	//VFace Register (backface lighting)
	o.vFace = IN.vFace;
}

采样主纹理，采样阴影纹理，主纹理和_Color混合，采样法线贴图，多了一个DiffTintMask值，计算边缘因子，还有一个从来没有见过的vface。

这个参考：https://docs.unity3d.com/Manual/SL-ShaderSemantics.html

A fragment shader can receive a variable that indicates whether the rendered surface is facing the camera
, or facing away from the camera. This is useful when rendering geometry that should be visible from both sides – often used on leaves and similar thin objects. The VFACE semantic input variable will contain a positive value for front-facing triangles, and a negative value for back-facing ones.

This feature only exists from shader model 3.0 onwards, so the shader needs to have the #pragma target 3.0 compilation directive.

这个值能揭示一个三角形是朝着相机的还是背着相机的。朝着相机的正面，vface>0；背着相机的,vface<0，unity官网提供了一个例子：

Shader "Unlit/Face Orientation"
{
    Properties
    {
        _ColorFront ("Front Color", Color) = (1,0.7,0.7,1)
        _ColorBack ("Back Color", Color) = (0.7,1,0.7,1)
    }
    SubShader
    {
        Pass
        {
            Cull Off // turn off backface culling

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 3.0

            float4 vert (float4 vertex : POSITION) : SV_POSITION
            {
                return UnityObjectToClipPos(vertex);
            }

            fixed4 _ColorFront;
            fixed4 _ColorBack;

            fixed4 frag (fixed facing : VFACE) : SV_Target
            {
                // VFACE input positive for frontbaces,
                // negative for backfaces. Output one
                // of the two colors depending on that.
                return facing > 0 ? _ColorFront : _ColorBack;
            }
            ENDCG
        }
    }
}