Unity Shader学习：相交算法实现简易防能量盾

主要思路：对比物体和场景深度图在观察空间下的深度差值，深度差越小表示相交，颜色越深，在加上边缘光勾出轮廓。

shader部分:

Shader "Unlit/DepthOutline"
{
 Properties{
 _MainTex("MainTex",2D) = "white"{}
 _RimFactor("RimFactor",Range(0.0,5.0))=1.0
 _DistanceFactor("DistanceFactor",Range(0.0,10.0))=1.0
 _RimColor("RimColor",Color)=(1,0,0,1)
 _DistanceFactor2("DistanceFactor2",Range(0.0,10.0))=1.0
 _DistanceFactor3("DistanceFactor3",Range(0.0,5.0)) = 1.0
 }
 SubShader{
 Tags{"Queue" = "Transparent" "RenderType" = "Transparent" "IgnoreProjector"="true"}
 Pass{
 Blend SrcAlpha OneMinusSrcAlpha
 ZWrite Off
 Cull Off
 CGPROGRAM
 #include "UnityCG.cginc"
 #pragma vertex vert
 #pragma fragment frag

 sampler2D _MainTex;
 float4 _MainTex_ST;
 sampler2D _CameraDepthTexture;
 float _RimFactor;
 float _DistanceFactor;
 float【文章来源：新加坡服务 欢迎留下您的宝贵建议】4 _RimColor;
 float _DistanceFactor2;
 float _DistanceFactor3;
 
 struct a2v {
 float4 vertex:POSITION;
 float2 uv:TEXCOORD0;
 float3 normal:NORMAL;
 };
 
 struct v2f {
 float2 uv:TEXCOORD0;
 float4 pos:SV_POSITION;
 float4 screenPos:TEXCOORD1;
 float3 worldNormal:TEXCOORD2;
 float3 worldViewDir:TEXCOORD3;
 };

 v2f vert(a2v v) {
 v2f o;
 o.pos = UnityObjectToClipPos(v.vertex);
 //ComputeScreenPos函数，得到归一化前的视口坐标xy
 //z分量为裁剪空间的z值，范围[-Near,Far]
 o.screenPos = ComputeScreenPos(o.pos);
 o.uv = TRANSFORM_TEX(v.uv,_MainTex);
 //COMPUTE_EYEDEPTH函数，将z分量范围[-Near,Far]转换为[Near,Far]
 COMPUTE_EYEDEPTH(o.screenPos.z);
 o.worldNormal = UnityObjectToWorldNormal(v.normal);
 o.worldViewDir = WorldSpaceViewDir(v.vertex).xyz;
 return o;
 }

 float4 frag(v2f i):SV_Target {
 float3 mainTex = 1-tex2D(_MainTex,i.uv).xyz;
 //获取深度纹理,通过LinearEyeDepth函数将采样的深度纹理值转换为对应的深度范围[Near~Far]
 float sceneZ = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE_PROJ(_CameraDepthTexture,UNITY_PROJ_COORD(i.screenPos)));
 //观察空间深度差,值越小颜色值越大
 float distance =1 - saturate(sceneZ - i.screenPos.z);
 //消除内部深度变化较大时产生的锯齿
 if (distance>0.999999)
 {
 distance = 0;
 }
 //调整深度差值的变化曲线
 distance = pow(saturate(_DistanceFactor * log(distance) + _DistanceFactor3), _DistanceFactor2);

 //角度越大边缘光越亮
 float rim =1 - abs(dot(normalize(i.worldNormal), normalize(i.worldViewDir)));
 rim = pow(rim, _RimFactor);
 float4 col = float4(0,0,0,0);
 col = lerp(col, float4(_RimColor.rgb,0.3), mainTex.r);
 //根据边缘光以及深度差渐变
 col = float4(_RimColor.rgb,lerp(col.a,_RimColor.a, distance));
 col = lerp(col, _RimColor, rim);
 return col;
 }

 ENDCG
 }
 }
}

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