When do _UseClipRect and _UseAlphaClip work in UI-Default.shader of newGUI?

Unity Engine
1

This is the code for “DefaultResourcesExtra/UI/UI-Default.shader” which is part of the Unity built-in shader that is most frequently used in our project.

Shader "UI/Default"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
      
        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255

        _ColorMask ("Color Mask", Float) = 15
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
      
        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }

        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Pass
        {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"
            #include "UnityUI.cginc"
          
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
            };
          
            fixed4 _Color;
            fixed4 _TextureSampleAdd;
  
            bool _UseClipRect;
            float4 _ClipRect;

            bool _UseAlphaClip;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.worldPosition = IN.vertex;
                OUT.vertex = mul(UNITY_MATRIX_MVP, OUT.worldPosition);

                OUT.texcoord = IN.texcoord;
              
                #ifdef UNITY_HALF_TEXEL_OFFSET
                OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
                #endif
              
                OUT.color = IN.color * _Color;
                return OUT;
            }

            sampler2D _MainTex;

            fixed4 frag(v2f IN) : SV_Target
            {
                half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;

                if (_UseClipRect)
                    color *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
              
                if (_UseAlphaClip)
                    clip (color.a - 0.001);

                return color;
            }
        ENDCG
        }
    }
}

We’ve changed the “frag” part of the code, and applied it to objects’ Mask and ScrollRect.
Since shader seems to worked the same in UnityEdior, we believe that UI/Mask uses a stencil feature.

            fixed4 frag(v2f IN) : SV_Target
            {
                half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
                return color;
            }

If so, we want to know when _UseClipRect and _UseAlphaClip properties work in shader code.
Also, we believe that if “if statement” is used in pixel shader there might be a performance reduction with low-end mobile devices.
Would using materials with custom build shader be the only solution to solve this problem?

2

_UseClipRect is used by the 2D Rect Mask and set to one when the 2D Rect Mask is enabled. The UI.Mask does in fact use the Stencil and does not use those two material properties.

1 Like
3

Thank you for helping me out, Stephan B!
I didn’t know they added the 2DRectMask in Unity 5.2 until now. Thank you!
If you don’t mind, I’ve got a few more questions.
Do you know how much it will affect the overall performance when fragment shader (pixel shader) is used in an “if statement” that does not work?
I checked this just now, and it seems that Unity 5.1 does not have if statement with frag shader.

Shader "UI/Default"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
      
        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255

        _ColorMask ("Color Mask", Float) = 15
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
      
        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }

        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Pass
        {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
          
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
            };
          
            fixed4 _Color;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                OUT.texcoord = IN.texcoord;
#ifdef UNITY_HALF_TEXEL_OFFSET
                OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
#endif
                OUT.color = IN.color * _Color;
                return OUT;
            }

            sampler2D _MainTex;

            fixed4 frag(v2f IN) : SV_Target
            {
                half4 color = tex2D(_MainTex, IN.texcoord) * IN.color;
                clip (color.a - 0.01);
                return color;
            }
        ENDCG
        }
    }
}

Does it have something to do with the Unity 5.2 performance upgrade that’s discussed here?
http://forum.unity3d.com/threads/very-poor-performance-on-android-after-upgrading-to-unity-5.306572/page-9

4

The linked thread is a huge collection of issues, ranging from user mistakes and misunderstandings to actual performance bugs. It is very likely that at least one of those many issues is the one you mentioned.

5

Thanks you Dantus.

6

Does anyone know how much it would affect the overall performance when “if statement” is used in a pixel shader?
I am currently avoiding performance reduction by using custom materials.

Is there any other way to avoid performance reduction?

Modified shader code:

Shader "Custom/UI/Default"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        _ColorMask ("Color Mask", Float) = 15
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Pass
        {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"
            #include "UnityUI.cginc"
           
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
            };
           
            fixed4 _Color;
            fixed4 _TextureSampleAdd;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.worldPosition = IN.vertex;
                OUT.vertex = mul(UNITY_MATRIX_MVP, OUT.worldPosition);

                OUT.texcoord = IN.texcoord;
               
                #ifdef UNITY_HALF_TEXEL_OFFSET
                OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
                #endif
               
                OUT.color = IN.color * _Color;
                return OUT;
            }

            sampler2D _MainTex;

            fixed4 frag(v2f IN) : SV_Target
            {
                return (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
            }
        ENDCG
        }
    }
}

Shader for UI/Mask’s objects:

Shader "Custom/UI/Default-Stencil"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
       
        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255

        _ColorMask ("Color Mask", Float) = 15
    }

    SubShader
    {
        Tags
        { 
            "Queue"="Transparent" 
            "IgnoreProjector"="True" 
            "RenderType"="Transparent" 
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
       
        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp] 
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }

        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Pass
        {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"
            #include "UnityUI.cginc"
           
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
            };
           
            fixed4 _Color;
            fixed4 _TextureSampleAdd;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.worldPosition = IN.vertex;
                OUT.vertex = mul(UNITY_MATRIX_MVP, OUT.worldPosition);

                OUT.texcoord = IN.texcoord;
               
                #ifdef UNITY_HALF_TEXEL_OFFSET
                OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
                #endif
               
                OUT.color = IN.color * _Color;
                return OUT;
            }

            sampler2D _MainTex;

            fixed4 frag(v2f IN) : SV_Target
            {
                return (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
            }
        ENDCG
        }
    }
}

Shader for UI/2DRectMask’s objects:

Shader "Custom/UI/Default-2DRectClip"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        _ColorMask ("Color Mask", Float) = 15
    }

    SubShader
    {
        Tags
        { 
            "Queue"="Transparent" 
            "IgnoreProjector"="True" 
            "RenderType"="Transparent" 
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }

        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Pass
        {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"
            #include "UnityUI.cginc"
           
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
            };
           
            fixed4 _Color;
            fixed4 _TextureSampleAdd;

            float4 _ClipRect;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.worldPosition = IN.vertex;
                OUT.vertex = mul(UNITY_MATRIX_MVP, OUT.worldPosition);

                OUT.texcoord = IN.texcoord;
               
                #ifdef UNITY_HALF_TEXEL_OFFSET
                OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
                #endif
               
                OUT.color = IN.color * _Color;
                return OUT;
            }

            sampler2D _MainTex;

            half4 frag(v2f IN) : SV_Target
            {
                return (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color * UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
            }
        ENDCG
        }
    }
}

Is defining each shader like the above the only way to optimize, and avoid performance reduction?

1 Like
7

i dont think the “if statement” is the problem, maybe the code inside of it is the problem.

In my game main menu i get 30 fps using the default ui shader, after using a custom shader much more simple i get up to 60fps. Even if there is any other way to improve peformance i think the custom shaders is the way to go.

This Shader for UI/2DRectMask’s objects that you wrote, improves the peformance? You tested it?

1 Like
8

@lassade , thanks for the reply.
I’ve used “Custom/UI/Default” shader and “Custom/UI/Default-Stencil” shader which I’ve posted above, and it has significantly improved the performance.
(Though it has not been properly tested.) Also, I have not tested “Custom/UI/Default-2DRectClip”. If you look at the UI Shader for the Unity 5.3 Beta release, you will find that they had stopped using the “if statement”