许多游戏使用非真实感渲染（NPR）的方法渲染游戏画面，例如卡通和水彩风格等；
卡通渲染
渲染轮廓线
这里使用过程式几何轮廓线渲染：使用两个Pass，第一个Pass使用轮廓线颜色渲染整个背面的面片，并在视角空间下把模型顶点沿着法线方向向外扩张一段距离，让背部轮廓线清晰可见；为了防止对于一些内凹的模型，背面面片遮挡正面面片的情况，在扩张背面顶点之前，先对顶点法线的z分量处理，使它们等于一个定值，然后把法线归一化后再对顶点扩张，使扩展后的背面更加扁平化，降低了遮挡正面面片的可能性。
优点是快速有效，适用于绝大多数表面平滑的模型，但不适合立方体这样平整的模型；
viewNormal.z=-0.5;
viewNormal=normalize(viewnormal);
viewPos=viewPos+viewNormal*_Outline;
高光
以往的高光模型不再可用，这里计算normal和halfDir的点乘结果，和一个阈值比较，为了防止高光边界出现锯齿，可以使用以下代码：
float spec=dot(worldNormal,worldHalfDir);
spec=lerp(0,1,smoothstep(-w,w,spec-threshold));
w是一个很小的值，当spec-threshold小于-w时，高光系数返回0，大于w时返回1，否则在0到1之间插值，这样可以使高光区域的边界处得到一个从0到1平滑变化的spec值；
这里使用领域像素之间的近似导数值，使用fwidth函数实现；
实现
// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "Unity Shaders Book/Chapter 14/Toon Shading" {
Properties {
_Color ("Color Tint", Color) = (1, 1, 1, 1)
_MainTex ("Main Tex", 2D) = "white" {
}
_Ramp ("Ramp Texture", 2D) = "white" {
} //控制漫反射色调的渐变纹理
_Outline ("Outline", Range(0, 1)) = 0.1 //控制轮廓线宽度
_OutlineColor ("Outline Color", Color) = (0, 0, 0, 1) //轮廓线颜色
_Specular ("Specular", Color) = (1, 1, 1, 1) //高光反射颜色
_SpecularScale ("Specular Scale", Range(0, 0.1)) = 0.01 //计算高光反射时使用的阈值
}
SubShader {
Tags {
"RenderType"="Opaque" "Queue"="Geometry"}
Pass {
NAME "OUTLINE"
//只渲染背面
Cull Front
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
float _Outline;
fixed4 _OutlineColor;
struct a2v {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct v2f {
float4 pos : SV_POSITION;
};
v2f vert (a2v v) {
v2f o;
//变化到视角空间是为了让描边在观察空间达到最好的效果
float4 pos = mul(UNITY_MATRIX_MV, v.vertex);
float3 normal = mul((float3x3)UNITY_MATRIX_IT_MV, v.normal);
normal.z = -0.5;
pos = pos + float4(normalize(normal), 0) * _Outline;
o.pos = mul(UNITY_MATRIX_P, pos);
return o;
}
float4 frag(v2f i) : SV_Target {
return float4(_OutlineColor.rgb, 1);
}
ENDCG
}
Pass {
Tags {
"LightMode"="ForwardBase" }
//渲染正面
Cull Back
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_fwdbase
#include "UnityCG.cginc"
#include "Lighting.cginc"
#include "AutoLight.cginc"
#include "UnityShaderVariables.cginc"
fixed4 _Color;
sampler2D _MainTex;
float4 _MainTex_ST;
sampler2D _Ramp;
fixed4 _Specular;
fixed _SpecularScale;
struct a2v {
float4 vertex : POSITION;
float3 normal : NORMAL;
float4 texcoord : TEXCOORD0;
float4 tangent : TANGENT;
};
struct v2f {
float4 pos : POSITION;
float2 uv : TEXCOORD0;
float3 worldNormal : TEXCOORD1;
float3 worldPos : TEXCOORD2;
SHADOW_COORDS(3)
};
v2f vert (a2v v) {
v2f o;
o.pos = UnityObjectToClipPos( v.vertex);
o.uv = TRANSFORM_TEX (v.texcoord, _MainTex);
o.worldNormal = UnityObjectToWorldNormal(v.normal);
o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
TRANSFER_SHADOW(o);
return o;
}
float4 frag(v2f i) : SV_Target {
fixed3 worldNormal = normalize(i.worldNormal);
fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
fixed3 worldViewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
fixed3 worldHalfDir = normalize(worldLightDir + worldViewDir);
fixed4 c = tex2D (_MainTex, i.uv);
fixed3 albedo = c.rgb * _Color.rgb;
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos);
//漫反射系数和阴影值相乘得到最终的漫反射系数
fixed diff = dot(worldNormal, worldLightDir);
diff = (diff * 0.5 + 0.5) * atten;
//对渐变纹理采样并和反射率、光照颜色相乘
fixed3 diffuse = _LightColor0.rgb * albedo * tex2D(_Ramp, float2(diff, diff)).rgb;
fixed spec = dot(worldNormal, worldHalfDir);
fixed w = fwidth(spec) * 2.0; //抗锯齿处理
//step是为了_SpecularScale=0时能完全消除高光反射的光照
fixed3 specular = _Specular.rgb * lerp(0, 1, smoothstep(-w, w, spec + _SpecularScale - 1)) * step(0.0001, _SpecularScale);
return fixed4(ambient + diffuse + specular, 1.0);
}
ENDCG
}
}
FallBack "Diffuse"
}
素描风格渲染
这里不采用mipmap，使用6张素描纹理渲染
// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
///
/// Reference: Praun E, Hoppe H, Webb M, et al. Real-time hatching[C]
/// Proceedings of the 28th annual conference on Computer graphics and interactive techniques. ACM, 2001: 581.
///
Shader "Unity Shaders Book/Chapter 14/Hatching" {
Properties {
_Color ("Color Tint", Color) = (1, 1, 1, 1)
_TileFactor ("Tile Factor", Float) = 1 //纹理平铺系数，值越大，素描线条越密
_Outline ("Outline", Range(0, 1)) = 0.1
//渲染时使用的6张纹理，线条密度一次增大
_Hatch0 ("Hatch 0", 2D) = "white" {
}
_Hatch1 ("Hatch 1", 2D) = "white" {
}
_Hatch2 ("Hatch 2", 2D) = "white" {
}
_Hatch3 ("Hatch 3", 2D) = "white" {
}
_Hatch4 ("Hatch 4", 2D) = "white" {
}
_Hatch5 ("Hatch 5", 2D) = "white" {
}
}
SubShader {
Tags {
"RenderType"="Opaque" "Queue"="Geometry"}
//必须大写，因为unity会自动把Pass名字转换成大写
UsePass "Unity Shaders Book/Chapter 14/Toon Shading/OUTLINE"
Pass {
Tags {
"LightMode"="ForwardBase" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_fwdbase
#include "UnityCG.cginc"
#include "Lighting.cginc"
#include "AutoLight.cginc"
#include "UnityShaderVariables.cginc"
fixed4 _Color;
float _TileFactor;
sampler2D _Hatch0;
sampler2D _Hatch1;
sampler2D _Hatch2;
sampler2D _Hatch3;
sampler2D _Hatch4;
sampler2D _Hatch5;
struct a2v {
float4 vertex : POSITION;
float4 tangent : TANGENT;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
//6张纹理的需要6个混合权重，存在两个fixed3中
fixed3 hatchWeights0 : TEXCOORD1;
fixed3 hatchWeights1 : TEXCOORD2;
//阴影效果使用
float3 worldPos : TEXCOORD3;
SHADOW_COORDS(4)
};
v2f vert(a2v v) {
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
//纹理采样坐标
o.uv = v.texcoord.xy * _TileFactor;
//计算漫反射系数
fixed3 worldLightDir = normalize(WorldSpaceLightDir(v.vertex));
fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
fixed diff = max(0, dot(worldLightDir, worldNormal));
//初始化权重
o.hatchWeights0 = fixed3(0, 0, 0);
o.hatchWeights1 = fixed3(0, 0, 0);
//把diff缩放[0,7],得到hatchFactor
float hatchFactor = diff * 7.0;
//将其分为7个子区间，判断所处区间计算混合权重
if (hatchFactor > 6.0) {
// Pure white, do nothing
} else if (hatchFactor > 5.0) {
o.hatchWeights0.x = hatchFactor - 5.0;
} else if (hatchFactor > 4.0) {
o.hatchWeights0.x = hatchFactor - 4.0;
o.hatchWeights0.y = 1.0 - o.hatchWeights0.x;
} else if (hatchFactor > 3.0) {
o.hatchWeights0.y = hatchFactor - 3.0;
o.hatchWeights0.z = 1.0 - o.hatchWeights0.y;
} else if (hatchFactor > 2.0) {
o.hatchWeights0.z = hatchFactor - 2.0;
o.hatchWeights1.x = 1.0 - o.hatchWeights0.z;
} else if (hatchFactor > 1.0) {
o.hatchWeights1.x = hatchFactor - 1.0;
o.hatchWeights1.y = 1.0 - o.hatchWeights1.x;
} else {
o.hatchWeights1.y = hatchFactor;
o.hatchWeights1.z = 1.0 - o.hatchWeights1.y;
}
o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
TRANSFER_SHADOW(o);
return o;
}
fixed4 frag(v2f i) : SV_Target {
//采样并和对应的权重相乘得到每张纹理的采样颜色
fixed4 hatchTex0 = tex2D(_Hatch0, i.uv) * i.hatchWeights0.x;
fixed4 hatchTex1 = tex2D(_Hatch1, i.uv) * i.hatchWeights0.y;
fixed4 hatchTex2 = tex2D(_Hatch2, i.uv) * i.hatchWeights0.z;
fixed4 hatchTex3 = tex2D(_Hatch3, i.uv) * i.hatchWeights1.x;
fixed4 hatchTex4 = tex2D(_Hatch4, i.uv) * i.hatchWeights1.y;
fixed4 hatchTex5 = tex2D(_Hatch5, i.uv) * i.hatchWeights1.z;
//计算纯白在渲染中的贡献度，通过1减去所有6张纹理的权重得到。是光照最亮的部分是纯白色
fixed4 whiteColor = fixed4(1, 1, 1, 1) * (1 - i.hatchWeights0.x - i.hatchWeights0.y - i.hatchWeights0.z -
i.hatchWeights1.x - i.hatchWeights1.y - i.hatchWeights1.z);
fixed4 hatchColor = hatchTex0 + hatchTex1 + hatchTex2 + hatchTex3 + hatchTex4 + hatchTex5 + whiteColor;
UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos);
return fixed4(hatchColor.rgb * _Color.rgb * atten, 1.0);
}
ENDCG
}
}
FallBack "Diffuse"
}