[shader]体积光影

最终效果

-------------------------------

思路

为了 投影出体积阴影，咱们多用一个pass来渲染网格。

网格延伸的方向是灯光的方向。

咱们将顶点转换到模型空间，而后计算和灯光的角度进行顶点的偏移。

btw:由于根据顶点偏移，因此不能对断开的顶点进行平滑的过分。

经过点乘插值咱们来决定颜色的插值。

该shader不只能够用来作体积投影，也能够在灯光下作体积光。

源代码

Shader "QQ/LightTrail"
{
	Properties
	{
		//_FrontColor("FrontColor",Color) = (0.5,0.5,0.5,1)
		_BackColor("BackColor",Color) = (0,0,0,1)
		_LightColor("LightColor",Color) = (1,1,0,1)
		_MainTex("Texture", 2D) = "white" {}
		_SmoothRange("SmoothRange",Range(0,20)) = 1
		_TrailColor("TrailColor",Color) = (0,0,0,1)
		_TrailPower("TrailPower",Range(0,10)) = 2
		_TrailLength("TrailLength",Range(0,500)) = 100
	}
		SubShader
	{
		Tags{ "RenderType" = "Transparent"
		"Queue" = "Transparent" }
		LOD 100
			Pass
		{
			Tags{ "LightMode" = "ForwardBase" }
			CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_fog
#include "UnityCG.cginc"
			struct a2v
		{
			float4 vertex : POSITION;
			float2 uv : TEXCOORD0;
			float3 normal:NORMAL;
		};

		struct v2f
		{
			float2 uv : TEXCOORD0;
			float4 vertex : SV_POSITION;
			float4 wPos:TEXCOORD1;
			UNITY_FOG_COORDS(2)
				float3 normal:TEXCOORD3;
			float2 uv_mask:TEXCOORD4;
		};

		uniform float4 _LightColor0;
		//fixed4 _FrontColor;
		fixed4 _BackColor;
		fixed4 _LightColor;
		sampler2D _MainTex;
		float4 _MainTex_ST;
		float _SmoothRange;
		v2f vert(a2v v)
		{
			v2f o;
			o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
			o.wPos = mul(unity_ObjectToWorld,v.vertex);
			_MainTex_ST.zw *= _Time.x;
			o.uv = TRANSFORM_TEX(v.uv, _MainTex);
			o.normal = UnityObjectToWorldNormal(v.normal);
			UNITY_TRANSFER_FOG(o,o.vertex);
			return o;
		}

		fixed4 frag(v2f i) : SV_Target
		{
			float nor = dot(i.normal, normalize(UnityWorldSpaceLightDir(i.wPos)));
		fixed4 col = tex2D(_MainTex, i.uv);
		float _front = saturate(nor*_SmoothRange);
		col *= lerp(_BackColor, _LightColor0,_front);
		col += _LightColor*min(1 - _front,col.a);
		UNITY_APPLY_FOG(i.fogCoord, col);
		return col;
		}
			ENDCG
		}
			Pass
		{
			Tags{ "LightMode" = "ForwardBase" }
			ZWrite Off
			Cull Off
			Blend SrcAlpha OneMinusSrcAlpha
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma multi_compile_fog
			#include "UnityCG.cginc"
			struct a2v
		{
			float4 vertex : POSITION;
			float3 normal:NORMAL;
		};

		struct v2f
		{
			float4 vertex : SV_POSITION;
			float3 wPos:TEXCOORD1;
			float3 normal:TEXCOORD2;
			UNITY_FOG_COORDS(3)
		};

		fixed4 _TrailColor;
		float _TrailPower;
		float _TrailLength;
		v2f vert(a2v v)
		{
			v2f o;
			o.wPos = mul(unity_ObjectToWorld,v.vertex);
			o.normal = UnityObjectToWorldNormal(v.normal);
			v.vertex.xyz += v.normal*0.01;
			o.vertex = mul(UNITY_MATRIX_M, v.vertex);
			float3 lightDir = normalize(UnityWorldSpaceLightDir(o.wPos));
			float NdotL = min(0,dot(o.normal, lightDir.xyz));
			o.vertex.xyz += lightDir *NdotL* _TrailLength;
			o.vertex = mul(UNITY_MATRIX_VP, o.vertex);
			UNITY_TRANSFER_FOG(o,o.vertex);
			return o;
		}

		fixed4 frag(v2f i) : SV_Target
		{
			float nor = dot(i.normal, normalize(UnityWorldSpaceLightDir(i.wPos)));
		fixed4 col = _TrailColor*(pow(1.5*_TrailColor.a - abs(nor), _TrailPower));
		UNITY_APPLY_FOG(i.fogCoord, col);
		return col;
		}
			ENDCG
		}
		Pass
	{
		Blend One One
		Tags{ "LightMode" = "ForwardAdd" }
		CGPROGRAM
		#pragma vertex vert
		#pragma fragment frag
		#pragma multi_compile_fog
		#include "UnityCG.cginc"
		struct a2v
		{
			float4 vertex : POSITION;
			float2 uv : TEXCOORD0;
			float3 normal:NORMAL;
		};

		struct v2f
		{
			float2 uv : TEXCOORD0;
			float4 vertex : SV_POSITION;
			float4 wPos:TEXCOORD1;
			UNITY_FOG_COORDS(2)
				float3 normal:TEXCOORD3;
			float2 uv_mask:TEXCOORD4;
		};

		uniform float4 _LightColor0;
		//fixed4 _FrontColor;
		fixed4 _BackColor;
		fixed4 _LightColor;
		sampler2D _MainTex;
		float4 _MainTex_ST;
		float _SmoothRange;
		v2f vert(a2v v)
		{
			v2f o;
			o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
			o.wPos = mul(unity_ObjectToWorld,v.vertex);
			_MainTex_ST.zw *= _Time.x;
			o.uv = TRANSFORM_TEX(v.uv, _MainTex);
			o.normal = UnityObjectToWorldNormal(v.normal);
			UNITY_TRANSFER_FOG(o,o.vertex);
			return o;
		}

		fixed4 frag(v2f i) : SV_Target
		{
			float nor = dot(i.normal, normalize(UnityWorldSpaceLightDir(i.wPos)));
			fixed4 col = tex2D(_MainTex, i.uv);
			float _front = saturate(nor*_SmoothRange);
			col *= lerp(_BackColor, _LightColor0,_front);
			col += _LightColor*min(1 - _front,col.a);
			UNITY_APPLY_FOG(i.fogCoord, col);
			return col;
		}
		ENDCG
	}
		Pass
		{
		Tags{ "LightMode" = "ForwardAdd" }
		ZWrite Off
		Cull Off
		Blend SrcAlpha OneMinusSrcAlpha
		CGPROGRAM
		#pragma vertex vert
		#pragma fragment frag
		#pragma multi_compile_fog
		#include "UnityCG.cginc"
		struct a2v
		{
			float4 vertex : POSITION;
			float3 normal:NORMAL;
		};

		struct v2f
		{
			float4 vertex : SV_POSITION;
			float3 wPos:TEXCOORD1;
			float3 normal:TEXCOORD2;
			UNITY_FOG_COORDS(3)
		};

		fixed4 _TrailColor;
		float _TrailPower;
		float _TrailLength;
		v2f vert(a2v v)
		{
			v2f o;
			o.wPos = mul(unity_ObjectToWorld,v.vertex);
			o.normal = UnityObjectToWorldNormal(v.normal);
			v.vertex.xyz += v.normal*0.01;
			o.vertex = mul(UNITY_MATRIX_M, v.vertex);
			float3 lightDir = normalize(UnityWorldSpaceLightDir(o.wPos));
			float NdotL = min(0,dot(o.normal, lightDir.xyz));
			o.vertex.xyz += lightDir *NdotL* _TrailLength;
			o.vertex = mul(UNITY_MATRIX_VP, o.vertex);
			UNITY_TRANSFER_FOG(o,o.vertex);
			return o;
		}

		fixed4 frag(v2f i) : SV_Target
		{
			float nor = dot(i.normal, normalize(UnityWorldSpaceLightDir(i.wPos)));
			fixed4 col = _TrailColor*(pow(1.5*_TrailColor.a - abs(nor), _TrailPower));
			UNITY_APPLY_FOG(i.fogCoord, col);
			return col;
		}
		ENDCG
		}
	}
}