效果展示：

原模型：

一、简单分析

卡通渲染又叫非真实渲染（None-Physical Rendering-NPR）,一般日漫里的卡通风格有几个特点：

1.人物有描边

2.有明显的阴影分界线，没有太平滑的过渡

以下就根据这两点来实现卡渲效果；

二、描边

1.法线外扩

实现描边方式多种，比如卷积区分边界；

这里使用更简单的两个Pass，一个只用纯色画背面，利用法线外扩顶点，根据深度的不同这个纯色的背面会被显示出来，同时又不会遮挡正面；

Pass
{
Tags {"LightMode"="ForwardBase"}
//裁剪正面，只画背面
Cull Front

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"

half _OutlineWidth;
half4 _OutLineColor;

struct a2v
{
float4 vertex : POSITION;
float3 normal : NORMAL;
float2 uv : TEXCOORD0;
float4 vertColor : COLOR;
float4 tangent : TANGENT;
};

struct v2f
{
float4 vertColor : TEXCOORD0;
float4 pos : SV_POSITION;
};

v2f vert (a2v v)
{
v2f o;
UNITY_INITIALIZE_OUTPUT(v2f, o);

//顶点沿着法线方向外扩
o.pos = UnityObjectToClipPos(float4(v.vertex.xyz + v.normal * _OutlineWidth * 0.1 ,1));

o.vertColor = fixed4(v.vertColor.rgb,1.0);
return o;
}

half4 frag(v2f i) : SV_TARGET
{
return half4(_OutLineColor.rgb * i.vertColor.rgb, 0);
}
ENDCG
}

2.细节处理（坑）

摄像机远近边缘线粗细不同

由于世界坐标系下做外扩，摄像机里物体远近会影响法线外扩的多少；

解决方案，在NDC坐标系下法线外扩；

//顶点着色器替换以下代码
float4 pos = UnityObjectToClipPos(v.vertex);

//摄像机空间法线
float3 viewNormal = mul((float3x3)UNITY_MATRIX_IT_MV, v.normal.xyz);

//将法线变换到NDC空间，投影空间*W分量
float3 ndcNormal = normalize(TransformViewToProjection(viewNormal.xyz)) * pos.w;

//xy两方向外扩
pos.xy += 0.01 * _OutlineWidth * ndcNormal.xy * v.vertColor.a;
o.pos = pos;

上下和左右边缘线粗细不同

NDC空间是正方形，而视口宽高比是长方体，导致描边上下和左右的粗细不统一；

解放方案，根据屏幕宽高比缩放法线再外扩；

//将近裁剪面右上角位置的顶点变换到观察空间
//unity_CameraInvProjection摄像机矩阵逆矩阵，UNITY_NEAR_CLIP_VALUE近截面值，DX：0，OpenGL-1.0;_ProjectionParams.y摄像机近截面
float4 nearUpperRight = mul(unity_CameraInvProjection, float4(1, 1, UNITY_NEAR_CLIP_VALUE, _ProjectionParams.y));

//求得屏幕宽高比
float aspect = abs(nearUpperRight.y / nearUpperRight.x);
ndcNormal.x *= aspect;

顶点重合法线不连续

模型顶点重合时会出现多条法线，在不同的面上法线不同导致描边不连续；

解决方案，修改模型顶点数据，同顶点多条法线求平均值；

需要和美工协商修改模型数据，这里写 3ff8 了脚本临时修改模型数据；

public class PlugTangentTools
{
[MenuItem("Tools/模型平均法线写入切线数据")]
public static void WirteAverageNormalToTangentToos()
{
MeshFilter[] meshFilters = Selection.activeGameObject.GetComponentsInChildren<MeshFilter>();
foreach (var meshFilter in meshFilters)
{
Mesh mesh = meshFilter.sharedMesh;
WirteAverageNormalToTangent(mesh);
}

SkinnedMeshRenderer[] skinMeshRenders = Selection.activeGameObject.GetComponentsInChildren<SkinnedMeshRenderer>();
foreach (var skinMeshRender in skinMeshRenders)
{
Mesh mesh = skinMeshRender.sharedMesh;
WirteAverageNormalToTangent(mesh);
}
Debug.Log("重合顶点平均法线写入成功");
}

private static void WirteAverageNormalToTangent(Mesh mesh)
{
var averageNormalHash = new Dictionary<Vector3, Vector3>();
for (var j = 0; j < mesh.vertexCount; j++)
{
if (!averageNormalHash.ContainsKey(mesh.vertices[j]))
{
averageNormalHash.Add(mesh.vertices[j], mesh.normals[j]);
}
else
{
averageNormalHash[mesh.vertices[j]] =
(averageNormalHash[mesh.vertices[j]] + mesh.normals[j]).normalized;
}
}

var averageNormals = new Vector3[mesh.vertexCount];
for (var j = 0; j < mesh.vertexCount; j++)
{
averageNormals[j] = averageNormalHash[mesh.vertices[j]];
}

var tangents = new Vector4[mesh.vertexCount];
for (var j = 0; j < mesh.vertexCount; j++)
{
tangents[j] = new Vector4(averageNormals[j].x, averageNormals[j].y, averageNormals[j].z, 0);
}
mesh.tangents = tangents;
}
}

细节处理前后对比：

ps：利用模型顶点的四个通道RGBA——对描边粗细显影相机距离缩放进行精细控制，需要美工配合；

三、着色

1.减少色阶

二分法

将有阴影和没阴影的地方做明显的区分；

half4 frag(v2f i) : SV_TARGET
{
half4 col = 1;
half4 mainTex = tex2D(_MainTex, i.uv);
half3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz);
half3 worldNormal = normalize(i.worldNormal);
half3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);

//半兰伯特光照模型
half halfLambert = dot(worldNormal, worldLightDir) * 0.5 + 0.5;

//_ShadowRange区分阴影范围，_ShadowSmooth控制分界线的柔和程度，求出ramp值（百分比）
half ramp = smoothstep(0, _ShadowSmooth, halfLambert - _ShadowRange);

//根据ramp值插值取样，将阴影和main颜色混合
half3 diffuse = lerp(_ShadowColor, _MainColor, ramp);
diffuse *= mainTex;
col.rgb = _LightColor0 * diffuse;
return col;
}

Ramp贴图

使用明显分界的色阶图来取样，使阴影有明显的分界线；

逻辑和二分一样，只是多加个几个色阶；

//_ShadowRange范围取样Ramp贴图
half ramp =  tex2D(_RampTex, float2(saturate(halfLambert - _ShadowRange), 0.5)).r;

​

高光色阶

卡渲高光和阴影一样，和周围色块有明显的分界线；

half3 specular = 0;
half3 halfDir = normalize(worldLightDir + viewDir);
half NdotH = max(0, dot(worldNormal, halfDir));
//_SpecularGloss控制高光光泽度
half SpecularSize = pow(NdotH, _SpecularGloss);

//_SpecularRange高光范围，_SpecularMulti强度，在范围内显示高光有明显分界
if (SpecularSize >= 1 - _SpecularRange)
{
specular = _SpecularMulti * _SpecularColor;
}

ilmTexture贴图

《GUILTY GEAR Xrd》中使用的方法，又叫Threshold贴图；

贴图的R通道控制漫反射的阴影阈值，G通道控制高光强度，B通道控制高光范围;

需要和美工配合，没贴图就不测了；

总之万物皆可用贴图来传递信息，rgba代表什么意思可以自行做各种trick；

half4 frag (v2f i) : SV_Target
{
half4 col = 0;
half4 mainTex = tex2D (_MainTex, i.uv);
//取样ilmTexture
half4 ilmTex = tex2D (_IlmTex, i.uv);
half3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz);
half3 worldNormal = normalize(i.worldNormal);
half3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);

//漫反射+阴影
half3 diffuse = 0;
half halfLambert = dot(worldNormal, worldLightDir) * 0.5 + 0.5;
//g通道控制高光强度
half threshold = (halfLambert + ilmTex.r) * 0.5;
half ramp = saturate(_ShadowRange  - threshold);
ramp =  smoothstep(0, _ShadowSmooth, ramp);
diffuse = lerp(_MainColor, _ShadowColor, ramp);
diffuse *= mainTex.rgb;

half3 specular = 0;
half3 halfDir = normalize(worldLightDir + viewDir);
half NdotH = max(0, dot(worldNormal, halfDir));
half SpecularSize = pow(NdotH, _SpecularGloss);
//b通道控制高光遮罩
half specularMask = ilmTex.b;
if (SpecularSize >= 1 - specularMask * _SpecularRange)
{
//g控制高光强度
specular = _SpecularMulti * (ilmTex.g) * _SpecularColor;
}

col.rgb = (diffuse + specular) * _LightColor0.rgb;
return col;
}

【翻译】西川善司「实验做出的游戏图形」「GUILTY GEAR Xrd -SIGN-」中实现的「纯卡通动画的实时3D图形」的秘密，前篇（1）

【翻译】西川善司「实验做出的游戏图形」「GUILTY GEAR Xrd -SIGN-」中实现的「纯卡通动画的实时3D图形」的秘密，前篇（2）

【翻译】西川善司的「实验做出的游戏图形」「GUILTY GEAR Xrd -SIGN-」中实现的「纯卡通动画的实时3D图形」的秘密，后篇

2.边缘泛光

三渲二加点边缘泛光会增加立体感，让画质更真实；效果如下；

_RimMin、_RimMax控制边缘泛光范围；

smoothstep使过渡平缓；再乘以RimColor，alpha控制强度；

half f =  1.0 - saturate(dot(viewDir, worldNormal));
half rim = smoothstep(_RimMin, _RimMax, f);
rim = smoothstep(0, _RimSmooth, rim);
half3 rimColor = rim * _RimColor.rgb *  _RimColor.a;
col.rgb = (diffuse + specular + rimColor) * _LightColor0.rgb;

3.mask遮罩图

用一张贴图来修正边缘泛光的效果；

边缘光的计算使用的是法线点乘视线。在物体的法线和视线垂直的时候，边缘光会很强。在球体上不会有问题，但是在一些有平面的物体，当平面和视线接近垂直的时候，会导致整个平面都有边缘光。这会让一些不该有边缘光的地方出现边缘光。

4.屏幕后效

post-processing官方组件中有bloom效果；

原理：提取图像中较亮区域，存储在纹理中，使用高斯模糊模拟光线扩散效果，将该纹理和原图像混合；过程比较复杂，后面写屏幕后期效果再分析吧；

完整Shader:

Shader "Unlit/CelRenderFull"
{
Properties
{
_MainTex ("MainTex", 2D) = "white" {}
_IlmTex ("IlmTex", 2D) = "white" {}

[Space(20)]
_MainColor("Main Color", Color) = (1,1,1)
_ShadowColor ("Shadow Color", Color) = (0.7, 0.7, 0.7)
_ShadowSmooth("Shadow Smooth", Range(0, 0.03)) = 0.002
_ShadowRange ("Shadow Range", Range(0, 1)) = 0.6

[Space(20)]
_SpecularColor("Specular Color", Color) = (1,1,1)
_SpecularRange ("Specular Range",  Range(0, 1)) = 0.9
_SpecularMulti ("Specular Multi", Range(0, 1)) = 0.4
_SpecularGloss("Sprecular Gloss", Range(0.001, 8)) = 4

[Space(20)]
_OutlineWidth ("Outline Width", Range(0, 1)) = 0.24
_OutLineColor ("OutLine Color", Color) = (0.5,0.5,0.5,1)

[Space(20)]
_RimMin	("imMin",float) = 1.0
_RimMax	("RimMax",float) = 2.0
_RimSmooth("RimSmooth",Range(0.0,1))=0.5
_RimColor("RimColor",Color) = (1,1,1,1)
}

SubShader
{
Pass
{
Tags { "LightMode"="ForwardBase"}

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_fwdbase

#include "UnityCG.cginc"
#include "Lighting.cginc"
#include "AutoLight.cginc"

sampler2D _MainTex;
float4 _MainTex_ST;
sampler2D _IlmTex;
float4 _IlmTex_ST;

half3 _MainColor;
half3 _ShadowColor;
half _ShadowSmooth;
half _ShadowRange;

half3 _SpecularColor;
half _SpecularRange;
half _SpecularMulti;
half _SpecularGloss;

half _RimMin;
half _RimMax;
half _RimSmooth;
fixed4 _RimColor;

struct a2v
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
float3 normal : NORMAL;
};

struct v2f
{
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
float3 worldNormal : TEXCOORD1;
float3 worldPos : TEXCOORD2;
};

v2f vert (a2v v)
{
v2f o = (v2f)0;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
o.worldNormal = UnityObjectToWorldNormal(v.normal);
o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
return o;
}

half4 frag (v2f i) : SV_Target
{
half4 col = 0;
half4 mainTex = tex2D (_MainTex, i.uv);
half4 ilmTex = tex2D (_IlmTex, i.uv);
half3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz);
half3 worldNormal = normalize(i.worldNormal);
half3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);

half3 diffuse = 0;
half halfLambert = dot(worldNormal, worldLightDir) * 0.5 + 0.5;
half threshold = (halfLambert + ilmTex.g) * 0.5;
half ramp = saturate(_ShadowRange  - threshold);
ramp =  smoothstep(0, _ShadowSmooth, ramp);
diffuse = lerp(_MainColor, _ShadowColor, ramp);
diffuse *= mainTex.rgb;

half3 specular = 0;
half3 halfDir = normalize(worldLightDir + viewDir);
half NdotH = max(0, dot(worldNormal, halfDir));
half SpecularSize = pow(NdotH, _SpecularGloss);
half specularMask = ilmTex.b;
if (SpecularSize >= 1 - specularMask * _SpecularRange)
{
specular = _SpecularMulti * (ilmTex.r) * _SpecularColor;
}

half f =  1.0 - saturate(dot(viewDir, worldNormal));
half rim = smoothstep(_RimMin, _RimMax, f);
rim = smoothstep(0, _RimSmooth, rim);
half3 rimColor = rim * _RimColor.rgb *  _RimColor.a;
col.rgb = (diffuse + specular + rimColor) * _LightColor0.rgb;
return col;
}
ENDCG
}

Pass
{
Tags {"LightMode"="ForwardBase"}

Cull Front

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"

half _OutlineWidth;
half4 _OutLineColor;

struct a2v
{
float4 vertex : POSITION;
float3 normal : NORMAL;
float2 uv : TEXCOORD0;
float4 vertColor : COLOR;
float4 tangent : TANGENT;
};

struct v2f

{
float4 vertColor : TEXCOORD0;
float4 pos : SV_POSITION;
};

v2f vert (a2v v)
{
v2f o;
UNITY_INITIALIZE_OUTPUT(v2f, o);

float4 pos = UnityObjectToClipPos(v.vertex);
float3 viewNormal = mul((float3x3)UNITY_MATRIX_IT_MV, v.tangent.xyz);
float3 ndcNormal = normalize(TransformViewToProjection(viewNormal.xyz)) * pos.w;

float4 nearUpperRight = mul(unity_CameraInvProjection, float4(1, 1, UNITY_NEAR_CLIP_VALUE, _ProjectionParams.y));
float aspect = abs(nearUpperRight.y / nearUpperRight.x);
ndcNormal.x *= aspect;

pos.xy += 0.01 * _OutlineWidth * ndcNormal.xy * v.vertColor.a;
o.pos = pos;
o.vertColor = fixed4(v.vertColor.rgb,1.0);
return o;
}

half4 frag(v2f i) : SV_TARGET
{
return half4(_OutLineColor.rgb * i.vertColor.rgb, 0);
}
ENDCG
}
}
FallBack Off
}