Untiy3d ShaderLab球体阴影(三) 点光源对球体的投影
发表于2017-05-06
本篇文章要介绍的是球体阴影中点光源对球体的投影，与平行光对平面的投影原理是一样的，具体方法大家可以看看代码部分是如何实现的。
如图所示，淡黄色的是阴影的淡入淡出，淡紫色的是点光源的阴影。在接受阴影的Shader 中计算了平行光和点光源两种阴影。与平行光对平面的投影原理差不多，这里就不多说了。
具体实现的是：
Shader "Tut/Shadow/SphereShadow_3" ｛
Properties ｛
_spPos ("Sphere Position", vector) = (0,0,0,1)
_spR ("Sphere Radius", float) = 1
_Intensity("Intensity Of Shadow",range(0,1))=0.5
｝
SubShader ｛
pass｛
Tags｛"LightMode"="ForwardBase"｝
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
float4 _spPos;
float _spR;
float _Intensity;
float4 _LightColor0;
struct v2f｛
float4 pos:SV_POSITION;
float3 litDir:TEXCOORD0;
float3 spDir:TEXCOORD1;
float4 vc:TEXCOORD2;
｝;
v2f vert(appdata_base v)
｛
v2f o;
o.pos=mul(UNITY_MATRIX_MVP,v.vertex);
o.litDir=WorldSpaceLightDir(v.vertex);
o.spDir=(_spPos-mul(_Object2World,v.vertex)).xyz;
float3 ldir=ObjSpaceLightDir(v.vertex);
ldir=normalize(ldir);
o.vc=_LightColor0*max(0,dot(ldir,v.normal));
return o;
｝
float4 frag(v2f i):COLOR
｛
float3 litDir=normalize(i.litDir);
float3 spDir=i.spDir;
float spDistance=length(spDir);
spDir=normalize(spDir);
float cosV=dot(spDir,litDir);
float sinV=sin(acos(max(0,cosV)));
float D=sinV*spDistance;
float shadow=step(_spR,D);//spR>D 0,else 1
float atten=pow((D/_spR),4);
float c=lerp(1-_Intensity,1,min(1,shadow+atten));//0 is dark //*step(0,dot(i.N,litDir))
return i.vc*c;
｝
ENDCG
｝//endpass
pass｛
Tags｛"LightMode"="ForwardAdd"｝
Blend One One
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
float4 _spPos;
float _spR;
float _Intensity;
float4 _LightColor0;
struct v2f｛
float4 pos:SV_POSITION;
float3 litDir:TEXCOORD0;
float3 spDir:TEXCOORD1;
float4 vc:TEXCOORD2;
｝;
v2f vert(appdata_base v)
｛
v2f o;
o.pos=mul(UNITY_MATRIX_MVP,v.vertex);
o.litDir=WorldSpaceLightDir(v.vertex);
o.spDir=(_spPos-mul(_Object2World,v.vertex)).xyz;
float3 ldir=ObjSpaceLightDir(v.vertex);
float atten=1/(1+length(ldir));
ldir=normalize(ldir);
o.vc=_LightColor0*max(0,dot(ldir,v.normal))*atten;
return o;
｝
float4 frag(v2f i):COLOR
｛
float litAtten=length(i.litDir);
float3 litDir=normalize(i.litDir);
float3 spDir=i.spDir;
float spDistance=length(spDir);
spDir=normalize(spDir);
float cosV=dot(spDir,litDir);
float sinV=sin(acos(max(0,cosV)));
float D=sinV*spDistance;
float shadow=step(0,D-_spR);//spR>D 0,else 1
float atten=pow((D/_spR),4);
float c=lerp(1-_Intensity,1,min(1,shadow+atten));//0 is dark //*step(0,dot(i.N,litDir))//
return c*i.vc;
｝
ENDCG
｝//endpass
｝
｝
