Shader “Universal Render Pipeline/NiloCat Extension/Screen Space Decal/Unlit”
{
Properties
{
[Header(Basic)]
_MainTex(“Texture”, 2D) = “white” {}
[HDR]_Color(“_Color (default = 1,1,1,1)”, color) = (1,1,1,1)
[Header(Blending)]
//https://docs.unity3d.com/ScriptReference/Rendering.BlendMode.html
[Enum(UnityEngine.Rendering.BlendMode)]_SrcBlend("_SrcBlend (default = SrcAlpha)", Float) = 5 //5 = SrcAlpha
[Enum(UnityEngine.Rendering.BlendMode)]_DstBlend("_DstBlend (default = OneMinusSrcAlpha)", Float) = 10 //10 = OneMinusSrcAlpha
[Header(Alpha remap(extra alpha control))]
_AlphaRemap("_AlphaRemap (default = 1,0,0,0) _____alpha will first mul x, then add y (zw unused)", vector) = (1,0,0,0)
[Header(Prevent Side Stretching(Compare projection direction with scene normal and Discard if needed))]
[Toggle(_ProjectionAngleDiscardEnable)] _ProjectionAngleDiscardEnable("_ProjectionAngleDiscardEnable (default = on)", float) = 1
_ProjectionAngleDiscardThreshold("_ProjectionAngleDiscardThreshold (default = 0)", range(-1,1)) = 0
[Header(Mul alpha to rgb)]
[Toggle]_MulAlphaToRGB("_MulAlphaToRGB (default = off)", Float) = 0
[Header(Ignore texture wrap mode setting)]
[Toggle(_FracUVEnable)] _FracUVEnable("_FracUVEnable (default = off)", Float) = 0
//====================================== below = usually can ignore in normal use case =====================================================================
[Header(Stencil Masking)]
//https://docs.unity3d.com/ScriptReference/Rendering.CompareFunction.html
_StencilRef("_StencilRef", Float) = 0
[Enum(UnityEngine.Rendering.CompareFunction)]_StencilComp("_StencilComp (default = Disable) _____Set to NotEqual if you want to mask by specific _StencilRef value, else set to Disable", Float) = 0 //0 = disable
[Header(ZTest)]
//https://docs.unity3d.com/ScriptReference/Rendering.CompareFunction.html
//default need to be Disable, because we need to make sure decal render correctly even if camera goes into decal cube volume, although disable ZTest by default will prevent EarlyZ (bad for GPU performance)
[Enum(UnityEngine.Rendering.CompareFunction)]_ZTest("_ZTest (default = Disable) _____to improve GPU performance, Set to LessEqual if camera never goes into cube volume, else set to Disable", Float) = 0 //0 = disable
[Header(Cull)]
//https://docs.unity3d.com/ScriptReference/Rendering.CullMode.html
//default need to be Front, because we need to make sure decal render correctly even if camera goes into decal cube
[Enum(UnityEngine.Rendering.CullMode)]_Cull("_Cull (default = Front) _____to improve GPU performance, Set to Back if camera never goes into cube volume, else set to Front", Float) = 1 //1 = Front
[Header(Unity Fog)]
[Toggle(_UnityFogEnable)] _UnityFogEnable("_UnityFogEnable (default = on)", Float) = 1
}
SubShader
{
Tags { "RenderType" = "Overlay" "Queue" = "AlphaTest+1" }
Pass
{
Stencil
{
Ref[_StencilRef]
Comp[_StencilComp]
}
Cull[_Cull]
ZTest[_ZTest]
ZWrite off
Blend[_SrcBlend][_DstBlend]
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
//due to using ddx() & ddy()
#pragma target 3.0
#pragma shader_feature_local _ProjectionAngleDiscardEnable
#pragma shader_feature_local _UnityFogEnable
#pragma shader_feature_local _FracUVEnable
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
};
struct v2f
{
float4 vertex : SV_POSITION;
#if _UnityFogEnable
UNITY_FOG_COORDS(1)
#endif
float4 screenUV : TEXCOORD0;
float4 viewRayOS : TEXCOORD2;
float3 cameraPosOS : TEXCOORD3;
};
CBUFFER_START(UnityPerMaterial)
sampler2D _MainTex;
float4 _MainTex_ST;
float _ProjectionAngleDiscardThreshold;
half4 _Color;
half2 _AlphaRemap;
half _MulAlphaToRGB;
CBUFFER_END
sampler2D _CameraDepthTexture;
v2f vert(appdata v)
{
v2f o;
//regular MVP
o.vertex = UnityObjectToClipPos(v.vertex);
//regular unity fog
#if _UnityFogEnable
UNITY_TRANSFER_FOG(o, o.vertex);
#endif
//prepare depth texture's screen space UV
o.screenUV = ComputeScreenPos(o.vertex);
//get "camera to vertex" ray in View space
float3 viewRay = UnityObjectToViewPos(v.vertex);
//***WARNING***
//=========================================================
//"viewRay z division" must do in the fragment shader, not vertex shader! (due to rasteriazation varying interpolation's perspective correction)
//We skip the "viewRay z division" in vertex shader for now, and pass the division value to varying o.viewRayOS.w first, we will do the division later when we enter fragment shader
//viewRay /= viewRay.z; //skip the "viewRay z division" in vertex shader for now
o.viewRayOS.w = viewRay.z;//pass the division value to varying o.viewRayOS.w
//=========================================================
viewRay *= -1; //unity's camera space is right hand coord(negativeZ pointing into screen), we want positive z ray in fragment shader, so negate it
//it is ok to write very expensive code in decal's vertex shader, it is just a unity cube(4*6 vertices) per decal only, won't affect GPU performance at all.
float4x4 ViewToObjectMatrix = mul(unity_WorldToObject, UNITY_MATRIX_I_V);
//transform everything to object space(decal space) in vertex shader first, so we can skip all matrix mul() in fragment shader
o.viewRayOS.xyz = mul((float3x3)ViewToObjectMatrix, viewRay);
o.cameraPosOS = mul(ViewToObjectMatrix, float4(0,0,0,1)).xyz;
return o;
}
half4 frag(v2f i) : SV_Target
{
//***WARNING***
//=========================================================
//now do "viewRay z division" that we skipped in vertex shader earlier.
i.viewRayOS /= i.viewRayOS.w;
//=========================================================
float sceneCameraSpaceDepth = LinearEyeDepth(tex2Dproj(_CameraDepthTexture, i.screenUV));
//scene depth in any space = rayStartPos + rayDir * rayLength
//here all data in ObjectSpace(OS) or DecalSpace
float3 decalSpaceScenePos = i.cameraPosOS + i.viewRayOS * sceneCameraSpaceDepth;
//convert unity cube's [-0.5,0.5] vertex pos range to [0,1] uv. Only works if you use unity cube in mesh filter!
float2 decalSpaceUV = decalSpaceScenePos.xy + 0.5;
//discard logic
//===================================================
// discard "out of cube volume" pixels
float mask = (abs(decalSpaceScenePos.x) < 0.5) * (abs(decalSpaceScenePos.y) < 0.5) * (abs(decalSpaceScenePos.z) < 0.5);
#if _ProjectionAngleDiscardEnable
// also discard "scene normal not facing decal projector direction" pixels
float3 decalSpaceHardNormal = normalize(cross(ddx(decalSpaceScenePos), ddy(decalSpaceScenePos)));//reconstruct scene hard normal using scene pos ddx&ddy
mask *= decalSpaceHardNormal.z > _ProjectionAngleDiscardThreshold;//compare scene hard normal with decal projector's dir, decalSpaceHardNormal.z equals dot(decalForwardDir,sceneHardNormalDir)
#endif
//call discard
clip(mask - 0.5);//if ZWrite is off, clip() is fast enough on mobile, because it won't write the DepthBuffer, so no pipeline stall(confirmed by ARM staff).
//===================================================
// sample the decal texture
float2 uv = decalSpaceUV.xy * _MainTex_ST.xy + _MainTex_ST.zw;//Texture tiling & offset
#if _FracUVEnable
uv = frac(uv);//add frac to ignore texture wrap setting
#endif
half4 col = tex2D(_MainTex, uv);
col *= _Color;//tint color
col.a = saturate(col.a * _AlphaRemap.x + _AlphaRemap.y);//alpha remap MAD
col.rgb *= lerp(1, col.a, _MulAlphaToRGB);//extra multiply alpha to RGB
#if _UnityFogEnable
// apply fog
UNITY_APPLY_FOG(i.fogCoord, col);
#endif
return col;
}
ENDCG
}
}
}