Shader学习的基础知识（二十九）素描风格渲染

版权声明：版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/ww1351646544/article/details/88587857

这里实现素描风格主要取使用的用几张笔触多少不要同的图来模拟手绘阴影的效果，图片来源于冯乐乐《Unity Shader入门精要》


我们这里用六张图通过光照计算出权重比例后传给片元着色器进行渲染。
解释都在代码里，有意思的例子可以细看一下代码：

Shader "Unity Shaders Book/Chapter 14/Hatching" {
	Properties {
		_Color ("Color Tint", Color) = (1, 1, 1, 1)
		//平铺系数
		_TileFactor ("Tile Factor", Float) = 1
		_Outline ("Outline", Range(0, 1)) = 0.1
		//声明了六张图
		_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"}
		
		//轮廓部分直接强用了上一自文章中的OUTLINE
		//Pass名字会转成大写的所以定就时最好也用大写，引用就必须大写了
		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;
				fixed3 hatchWeights0 : TEXCOORD1;
				fixed3 hatchWeights1 : TEXCOORD2;
				float3 worldPos : TEXCOORD3;
				SHADOW_COORDS(4)
			};
			
			v2f vert(a2v v) {
				v2f o;
				
				o.pos = UnityObjectToClipPos(v.vertex);
				
				o.uv = v.texcoord.xy * _TileFactor;
				
				//正常计算光照
				fixed3 worldLightDir = normalize(WorldSpaceLightDir(v.vertex));
				fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
				fixed diff = max(0, dot(worldLightDir, worldNormal));
				
				o.hatchWeights0 = fixed3(0, 0, 0);
				o.hatchWeights1 = fixed3(0, 0, 0);
				
				//光照乘7，好用来划分7个亮度等级
				float hatchFactor = diff * 7.0;
				
				//下面是各等级划分
				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;
				}
				
				//顶点坐标转世界
				o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
				
				TRANSFER_SHADOW(o);
				
				return o; 
			}
			
			fixed4 frag(v2f i) : SV_Target {		
				//六张图的纹素采样
				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;
				//用白色去减这这个点在的权重，因为剩下的位置都得是白色
				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);
				//六张图的权重加上白色得到最终颜色
				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"
}