Context: If you google for Hidden/Fatblur, you'll find multiple urls where this shader is available, i won't post any link here because i don't know where the original is located. It's basically a shader for blurring that should be optimized for mobile devices.
Problem: If you used this shader in the past and just updated your Unity version to 2018+, the shader stops working.
What i tried: I messed up the shader in the Editor... hear the god news, was able to get the same symptoms. So I know the issue is in the way this shader is compiled on my iOS device. No shader errors though during the unity ->x Code project compilation.
Question: How do I fix the shader such that it works again?
Here is the shader code that is not working:
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "Hidden/FastBlur" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_Bloom ("Bloom (RGB)", 2D) = "black" {}
}
CGINCLUDE
#include "UnityCG.cginc"
sampler2D _MainTex;
sampler2D _Bloom;
uniform half4 _MainTex_TexelSize;
half4 _MainTex_ST;
half4 _Bloom_ST;
uniform half4 _Parameter;
struct v2f_tap
{
float4 pos : SV_POSITION;
half2 uv20 : TEXCOORD0;
half2 uv21 : TEXCOORD1;
half2 uv22 : TEXCOORD2;
half2 uv23 : TEXCOORD3;
};
v2f_tap vert4Tap ( appdata_img v )
{
v2f_tap o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv20 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy, _MainTex_ST);
o.uv21 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy * half2(-0.5h,-0.5h), _MainTex_ST);
o.uv22 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy * half2(0.5h,-0.5h), _MainTex_ST);
o.uv23 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy * half2(-0.5h,0.5h), _MainTex_ST);
return o;
}
fixed4 fragDownsample ( v2f_tap i ) : SV_Target
{
fixed4 color = tex2D (_MainTex, i.uv20);
color += tex2D (_MainTex, i.uv21);
color += tex2D (_MainTex, i.uv22);
color += tex2D (_MainTex, i.uv23);
return color / 4;
}
// weight curves
static const half curve[7] = { 0.0205, 0.0855, 0.232, 0.324, 0.232, 0.0855, 0.0205 }; // gauss'ish blur weights
static const half4 curve4[7] = { half4(0.0205,0.0205,0.0205,0), half4(0.0855,0.0855,0.0855,0), half4(0.232,0.232,0.232,0),
half4(0.324,0.324,0.324,1), half4(0.232,0.232,0.232,0), half4(0.0855,0.0855,0.0855,0), half4(0.0205,0.0205,0.0205,0) };
struct v2f_withBlurCoords8
{
float4 pos : SV_POSITION;
half4 uv : TEXCOORD0;
half2 offs : TEXCOORD1;
};
struct v2f_withBlurCoordsSGX
{
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
half4 offs[3] : TEXCOORD1;
};
v2f_withBlurCoords8 vertBlurHorizontal (appdata_img v)
{
v2f_withBlurCoords8 o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = half4(v.texcoord.xy,1,1);
o.offs = _MainTex_TexelSize.xy * half2(1.0, 0.0) * _Parameter.x;
return o;
}
v2f_withBlurCoords8 vertBlurVertical (appdata_img v)
{
v2f_withBlurCoords8 o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = half4(v.texcoord.xy,1,1);
o.offs = _MainTex_TexelSize.xy * half2(0.0, 1.0) * _Parameter.x;
return o;
}
half4 fragBlur8 ( v2f_withBlurCoords8 i ) : SV_Target
{
half2 uv = i.uv.xy;
half2 netFilterWidth = i.offs;
half2 coords = uv - netFilterWidth * 3.0;
half4 color = 0;
for( int l = 0; l < 7; l++ )
{
half4 tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[l];
coords += netFilterWidth;
}
return color;
}
v2f_withBlurCoordsSGX vertBlurHorizontalSGX (appdata_img v)
{
v2f_withBlurCoordsSGX o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = UnityStereoScreenSpaceUVAdjust(v.texcoord.xy, _MainTex_ST);
half offsetMagnitude = _MainTex_TexelSize.x * _Parameter.x;
o.offs[0] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(-3.0h, 0.0h, 3.0h, 0.0h), _MainTex_ST);
o.offs[1] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(-2.0h, 0.0h, 2.0h, 0.0h), _MainTex_ST);
o.offs[2] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(-1.0h, 0.0h, 1.0h, 0.0h), _MainTex_ST);
return o;
}
v2f_withBlurCoordsSGX vertBlurVerticalSGX (appdata_img v)
{
v2f_withBlurCoordsSGX o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = half4(UnityStereoScreenSpaceUVAdjust(v.texcoord.xy, _MainTex_ST),1,1);
half offsetMagnitude = _MainTex_TexelSize.y * _Parameter.x;
o.offs[0] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(0.0h, -3.0h, 0.0h, 3.0h), _MainTex_ST);
o.offs[1] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(0.0h, -2.0h, 0.0h, 2.0h), _MainTex_ST);
o.offs[2] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(0.0h, -1.0h, 0.0h, 1.0h), _MainTex_ST);
return o;
}
half4 fragBlurSGX ( v2f_withBlurCoordsSGX i ) : SV_Target
{
half2 uv = i.uv.xy;
half4 color = tex2D(_MainTex, i.uv) * curve4[3];
for( int l = 0; l < 3; l++ )
{
half4 tapA = tex2D(_MainTex, i.offs[l].xy);
half4 tapB = tex2D(_MainTex, i.offs[l].zw);
color += (tapA + tapB) * curve4[l];
}
return color;
}
ENDCG
SubShader {
ZTest Off Cull Off ZWrite Off Blend Off
// 0
Pass {
CGPROGRAM
#pragma vertex vert4Tap
#pragma fragment fragDownsample
ENDCG
}
// 1
Pass {
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurVertical
#pragma fragment fragBlur8
ENDCG
}
// 2
Pass {
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurHorizontal
#pragma fragment fragBlur8
ENDCG
}
// alternate blur
// 3
Pass {
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurVerticalSGX
#pragma fragment fragBlurSGX
ENDCG
}
// 4
Pass {
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurHorizontalSGX
#pragma fragment fragBlurSGX
ENDCG
}
}
FallBack Off
}
The answer is to unroll the for loops:
There are 2 loops (one of size 3, and one of size 7)
Just unroll them manually, replacing [l] with [0] etc.
The shader now gets properly compiled and you get the desired results again on your iOS device!
Here is the modified shader code such that it works:
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "Hidden/FastBlur"
{
Properties
{
_MainTex ("Base (RGB)", 2D) = "white" {}
_Bloom ("Bloom (RGB)", 2D) = "black" {}
}
CGINCLUDE
#include "UnityCG.cginc"
sampler2D _MainTex;
sampler2D _Bloom;
uniform half4 _MainTex_TexelSize;
half4 _MainTex_ST;
half4 _Bloom_ST;
uniform half4 _Parameter;
struct v2f_tap
{
float4 pos : SV_POSITION;
half2 uv20 : TEXCOORD0;
half2 uv21 : TEXCOORD1;
half2 uv22 : TEXCOORD2;
half2 uv23 : TEXCOORD3;
};
v2f_tap vert4Tap ( appdata_img v )
{
v2f_tap o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv20 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy, _MainTex_ST);
o.uv21 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy * half2(-0.5h,-0.5h), _MainTex_ST);
o.uv22 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy * half2(0.5h,-0.5h), _MainTex_ST);
o.uv23 = UnityStereoScreenSpaceUVAdjust(v.texcoord + _MainTex_TexelSize.xy * half2(-0.5h,0.5h), _MainTex_ST);
return o;
}
fixed4 fragDownsample ( v2f_tap i ) : SV_Target
{
fixed4 color = tex2D (_MainTex, i.uv20);
color += tex2D (_MainTex, i.uv21);
color += tex2D (_MainTex, i.uv22);
color += tex2D (_MainTex, i.uv23);
return color / 4;
}
// weight curves
static const half curve[7] = { 0.0205, 0.0855, 0.232, 0.324, 0.232, 0.0855, 0.0205 }; // gauss'ish blur weights
static const half4 curve4[7] = { half4(0.0205,0.0205,0.0205,0), half4(0.0855,0.0855,0.0855,0), half4(0.232,0.232,0.232,0),
half4(0.324,0.324,0.324,1), half4(0.232,0.232,0.232,0), half4(0.0855,0.0855,0.0855,0), half4(0.0205,0.0205,0.0205,0) };
struct v2f_withBlurCoords8
{
float4 pos : SV_POSITION;
half4 uv : TEXCOORD0;
half2 offs : TEXCOORD1;
};
struct v2f_withBlurCoordsSGX
{
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
half4 offs[3] : TEXCOORD1;
};
v2f_withBlurCoords8 vertBlurHorizontal (appdata_img v)
{
v2f_withBlurCoords8 o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = half4(v.texcoord.xy,1,1);
o.offs = _MainTex_TexelSize.xy * half2(1.0, 0.0) * _Parameter.x;
return o;
}
v2f_withBlurCoords8 vertBlurVertical (appdata_img v)
{
v2f_withBlurCoords8 o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = half4(v.texcoord.xy,1,1);
o.offs = _MainTex_TexelSize.xy * half2(0.0, 1.0) * _Parameter.x;
return o;
}
half4 fragBlur8 ( v2f_withBlurCoords8 i ) : SV_Target
{
half2 uv = i.uv.xy;
half2 netFilterWidth = i.offs;
half2 coords = uv - netFilterWidth * 3.0;
half4 color = 0;
//for( int l = 0; l < 7; l++ )
half4 tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[0];
coords += netFilterWidth;
tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[1];
coords += netFilterWidth;
tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[2];
coords += netFilterWidth;
tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[3];
coords += netFilterWidth;
tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[4];
coords += netFilterWidth;
tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[5];
coords += netFilterWidth;
tap = tex2D(_MainTex, UnityStereoScreenSpaceUVAdjust(coords, _MainTex_ST));
color += tap * curve4[6];
coords += netFilterWidth;
return color;
}
v2f_withBlurCoordsSGX vertBlurHorizontalSGX (appdata_img v)
{
v2f_withBlurCoordsSGX o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = UnityStereoScreenSpaceUVAdjust(v.texcoord.xy, _MainTex_ST);
half offsetMagnitude = _MainTex_TexelSize.x * _Parameter.x;
o.offs[0] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(-3.0h, 0.0h, 3.0h, 0.0h), _MainTex_ST);
o.offs[1] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(-2.0h, 0.0h, 2.0h, 0.0h), _MainTex_ST);
o.offs[2] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(-1.0h, 0.0h, 1.0h, 0.0h), _MainTex_ST);
return o;
}
v2f_withBlurCoordsSGX vertBlurVerticalSGX (appdata_img v)
{
v2f_withBlurCoordsSGX o;
o.pos = UnityObjectToClipPos (v.vertex);
o.uv = half4(UnityStereoScreenSpaceUVAdjust(v.texcoord.xy, _MainTex_ST),1,1);
half offsetMagnitude = _MainTex_TexelSize.y * _Parameter.x;
o.offs[0] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(0.0h, -3.0h, 0.0h, 3.0h), _MainTex_ST);
o.offs[1] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(0.0h, -2.0h, 0.0h, 2.0h), _MainTex_ST);
o.offs[2] = UnityStereoScreenSpaceUVAdjust(v.texcoord.xyxy + offsetMagnitude * half4(0.0h, -1.0h, 0.0h, 1.0h), _MainTex_ST);
return o;
}
half4 fragBlurSGX ( v2f_withBlurCoordsSGX i ) : SV_Target
{
half2 uv = i.uv.xy;
half4 color = tex2D(_MainTex, i.uv) * curve4[3];
//for( int l = 0; l < 3; l++ )
half4 tapA = tex2D(_MainTex, i.offs[0].xy);
half4 tapB = tex2D(_MainTex, i.offs[0].zw);
color += (tapA + tapB) * curve4[0];
tapA = tex2D(_MainTex, i.offs[1].xy);
tapB = tex2D(_MainTex, i.offs[1].zw);
color += (tapA + tapB) * curve4[1];
tapA = tex2D(_MainTex, i.offs[2].xy);
tapB = tex2D(_MainTex, i.offs[2].zw);
color += (tapA + tapB) * curve4[2];
return color;
}
ENDCG
SubShader
{
ZTest Off Cull Off ZWrite Off Blend Off
// 0
Pass
{
CGPROGRAM
#pragma vertex vert4Tap
#pragma fragment fragDownsample
ENDCG
}
// 1
Pass
{
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurVertical
#pragma fragment fragBlur8
ENDCG
}
// 2
Pass
{
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurHorizontal
#pragma fragment fragBlur8
ENDCG
}
// alternate blur
// 3
Pass
{
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurVerticalSGX
#pragma fragment fragBlurSGX
ENDCG
}
// 4
Pass
{
ZTest Always
Cull Off
CGPROGRAM
#pragma vertex vertBlurHorizontalSGX
#pragma fragment fragBlurSGX
ENDCG
}
}
FallBack Off
}