Hi I encountered a strange graphical bug with Screen Space - Overlay for my custom UI Image shader.
I set my player to become a child of an object it’s standing on so that it moves with it when the parent object is moved. Under my player is my UI canvas, which uses screen space - overlay. Whenever my player is on a moving object, I get graphical glitches on custom transparent effects like this. It changes every frame the object is moved.
In this example I use a custom UI which essentially is just a grab pass blur. This doesn’t appear when using Screen Space - Camera, but I’m too far along in my project to make a big change like that because it relies on overlay coordinates.
Here’s the code:
Shader "Ahlquist Interactive/SimpleGrabPassBlur" {
Properties{
_Color("Main Color", Color) = (1,1,1,1)
_BumpAmt("Distortion", Range(0,128)) = 10
_MainTex("Tint Color (RGB)", 2D) = "white" {}
_BumpMap("Normalmap", 2D) = "bump" {}
_Size("Size", Range(0, 50)) = 1
}
Category{
// We must be transparent, so other objects are drawn before this one.
Tags { "Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Opaque" }
Cull Off
SubShader {
// Horizontal blur
GrabPass {
Tags { "LightMode" = "Always" }
}
Pass {
Tags { "LightMode" = "Always" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma fragmentoption ARB_precision_hint_fastest
#include "UnityCG.cginc"
struct appdata_t {
float4 vertex : POSITION;
float2 texcoord: TEXCOORD0;
};
struct v2f {
float4 vertex : POSITION;
float4 uvgrab : TEXCOORD0;
};
v2f vert(appdata_t v) {
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
#if UNITY_UV_STARTS_AT_TOP
float scale = -1.0;
#else
float scale = 1.0;
#endif
o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;
o.uvgrab.zw = o.vertex.zw;
return o;
}
sampler2D _GrabTexture;
float4 _GrabTexture_TexelSize;
float _Size;
half4 frag(v2f i) : COLOR {
// half4 col = tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
// return col;
half4 sum = half4(0,0,0,0);
#define GRABPIXEL(weight,kernelx) tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(float4(i.uvgrab.x + _GrabTexture_TexelSize.x * kernelx*_Size, i.uvgrab.y, i.uvgrab.z, i.uvgrab.w))) * weight
sum += GRABPIXEL(0.05, -4.0);
sum += GRABPIXEL(0.09, -3.0);
sum += GRABPIXEL(0.12, -2.0);
sum += GRABPIXEL(0.15, -1.0);
sum += GRABPIXEL(0.18, 0.0);
sum += GRABPIXEL(0.15, +1.0);
sum += GRABPIXEL(0.12, +2.0);
sum += GRABPIXEL(0.09, +3.0);
sum += GRABPIXEL(0.05, +4.0);
return sum;
}
ENDCG
}
// Vertical blur
GrabPass {
Tags { "LightMode" = "Always" }
}
Pass {
Tags { "LightMode" = "Always" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma fragmentoption ARB_precision_hint_fastest
#include "UnityCG.cginc"
struct appdata_t {
float4 vertex : POSITION;
float2 texcoord: TEXCOORD0;
};
struct v2f {
float4 vertex : POSITION;
float4 uvgrab : TEXCOORD0;
};
v2f vert(appdata_t v) {
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
#if UNITY_UV_STARTS_AT_TOP
float scale = -1.0;
#else
float scale = 1.0;
#endif
o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;
o.uvgrab.zw = o.vertex.zw;
return o;
}
sampler2D _GrabTexture;
float4 _GrabTexture_TexelSize;
float _Size;
half4 frag(v2f i) : COLOR {
// half4 col = tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
// return col;
half4 sum = half4(0,0,0,0);
#define GRABPIXEL(weight,kernely) tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(float4(i.uvgrab.x, i.uvgrab.y + _GrabTexture_TexelSize.y * kernely*_Size, i.uvgrab.z, i.uvgrab.w))) * weight
//G(X) = (1/(sqrt(2*PI*deviation*deviation))) * exp(-(x*x / (2*deviation*deviation)))
sum += GRABPIXEL(0.05, -4.0);
sum += GRABPIXEL(0.09, -3.0);
sum += GRABPIXEL(0.12, -2.0);
sum += GRABPIXEL(0.15, -1.0);
sum += GRABPIXEL(0.18, 0.0);
sum += GRABPIXEL(0.15, +1.0);
sum += GRABPIXEL(0.12, +2.0);
sum += GRABPIXEL(0.09, +3.0);
sum += GRABPIXEL(0.05, +4.0);
return sum;
}
ENDCG
}
// Distortion
GrabPass {
Tags { "LightMode" = "Always" }
}
Pass {
Tags { "LightMode" = "Always" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma fragmentoption ARB_precision_hint_fastest
#pragma debug
#include "UnityCG.cginc"
struct appdata_t {
float4 vertex : POSITION;
float2 texcoord: TEXCOORD0;
};
struct v2f {
float4 vertex : POSITION;
float4 uvgrab : TEXCOORD0;
float2 uvbump : TEXCOORD1;
float2 uvmain : TEXCOORD2;
};
float _BumpAmt;
float4 _BumpMap_ST;
float4 _MainTex_ST;
v2f vert(appdata_t v) {
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
#if UNITY_UV_STARTS_AT_TOP
float scale = -1.0;
#else
float scale = 1.0;
#endif
o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;
o.uvgrab.zw = o.vertex.zw;
o.uvbump = TRANSFORM_TEX(v.texcoord, _BumpMap);
o.uvmain = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}
fixed4 _Color;
sampler2D _GrabTexture;
float4 _GrabTexture_TexelSize;
sampler2D _BumpMap;
sampler2D _MainTex;
half4 frag(v2f i) : COLOR {
// calculate perturbed coordinates
half2 bump = UnpackNormal(tex2D(_BumpMap, i.uvbump)).rg; // we could optimize this by just reading the x y without reconstructing the Z
float2 offset = bump * _BumpAmt * _GrabTexture_TexelSize.xy;
i.uvgrab.xy = offset * i.uvgrab.z + i.uvgrab.xy;
half4 col = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
half4 tint = tex2D(_MainTex, i.uvmain) * _Color;
return col * tint;
}
ENDCG
}
}
}
}
Anyone can identify what might cause a graphical glitch like this? Thank you
and I’m sorry if this isn’t the right board, not sure if it’s actually 100% shader or UGui related…