Why Do Android Devices Hate This Shader?

[Ferazel]

Hi,

I've just started Unity Android development and found out that one of the modified shaders that our project is using is causing the devices to crash.

The shader is a modified cutout soft-edge shader. I removed the color component out of the shader computation (at least I think I did) because I didn't need to do any color modulation.

When using the vanilla Soft-Edge shader it works fine, but only when I try to use this optimized soft-edge shader I run into problems. For now I'm just using the vanilla one. However, is there a reason why this version doesn't work? It works fine in the Editor, it just creates a Signal 11 crash when I run it on my HTC Nexus One device. Any help would be appreciated so that I can better understand what I did wrong.

Thanks!

Properties {
    _MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
    _Cutoff ("Base Alpha cutoff", Range (0,.9)) = .5
}

SubShader {
    Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="TransparentCutout" }
    Lighting off

    // first pass:
    //   render any pixels that are more than [_Cutoff] opaque
    Pass {  
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata_t {
                float4 vertex : POSITION;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f {
                float4 vertex : POSITION;
                float2 texcoord : TEXCOORD0;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _Cutoff;

            v2f vert (appdata_t v)
            {
                v2f o;
                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
                return o;
            }

            float4 _Color;
            half4 frag (v2f i) : COLOR
            {
                half4 col = tex2D(_MainTex, i.texcoord);
                clip(col.a - _Cutoff);
                return col;
            }
        ENDCG
    }

    // Second pass:
    //   render the semitransparent details.
    Pass {
        Tags { "RequireOption" = "SoftVegetation" }

        // Dont write to the depth buffer
        ZWrite off

        // Set up alpha blending
        Blend SrcAlpha OneMinusSrcAlpha

        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata_t {
                float4 vertex : POSITION;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f {
                float4 vertex : POSITION;
                float2 texcoord : TEXCOORD0;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _Cutoff;

            v2f vert (appdata_t v)
            {
                v2f o;
                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
                return o;
            }

            float4 _Color;
            half4 frag (v2f i) : COLOR
            {
                half4 col = tex2D(_MainTex, i.texcoord);
                clip(-(col.a - _Cutoff));
                return col;
            }
        ENDCG
    }
}

SubShader {
    Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="TransparentCutout" }
    Lighting off

    // first pass:
    //   render any pixels that are more than [_Cutoff] opaque
    Pass {  
        AlphaTest Greater [_Cutoff]
        SetTexture [_MainTex] {
            combine texture 
        }
    }

    // Second pass:
    //   render the semitransparent details.
    Pass {
        // Dont write to the depth buffer
        ZWrite off

        // Only render pixels less or equal to the value
        AlphaTest LEqual [_Cutoff]

        // Set up alpha blending
        Blend SrcAlpha OneMinusSrcAlpha

        SetTexture [_MainTex] {
            Combine texture 
        }
    }
}

[Jessy]

This does not answer your question, but here's what I was talking about, in my comment (sorry, I don't know Cg or feel a need to learn it presently):

Shader "Transparent/Cutout/Soft Edge Unlit +" {

Properties {
    _MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
    _Cutoff ("Base Alpha cutoff  (Use Script)", Float) = 1
    _CutoffInverseQuarter ("Cutoff inverse / 4  (Use Script)", Float) = 1
}

Category {
    Tags {"Queue"="AlphaTest" "IgnoreProjector"="True" "RenderType"="TransparentCutout"}

    SubShader {
        Pass {
            GLSLPROGRAM
            varying mediump vec2 uv;

            #ifdef VERTEX
            void main() {
                gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
                uv = gl_MultiTexCoord0.xy;
            }
            #endif

            #ifdef FRAGMENT
            uniform lowp sampler2D _MainTex;
            uniform lowp float _Cutoff;
            void main() {
                vec4 texture = texture2D(_MainTex, uv);
                if (texture.a < _Cutoff) discard;
                gl_FragColor = texture;
            }
            #endif      
            ENDGLSL
        }
        Pass {
            ZTest Less  ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha

            GLSLPROGRAM
            varying mediump vec2 uv;

            #ifdef VERTEX
            void main() {
                gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
                uv = gl_MultiTexCoord0.xy;
            }
            #endif

            #ifdef FRAGMENT
            uniform lowp sampler2D _MainTex;
            uniform lowp float _Cutoff;
            void main() {
                vec4 texture = texture2D(_MainTex, uv);
                gl_FragColor = vec4(texture.rgb, texture.a / _Cutoff);
            }
            #endif      
            ENDGLSL
        }   
    }

    SubShader {
        Pass {
            AlphaTest GEqual[_Cutoff]
            SetTexture[_MainTex]
        }
        Pass {
            ZTest Less  ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha
            SetTexture[_MainTex] {
                ConstantColor(0,0,0, [_CutoffInverseQuarter])
                Combine texture, texture * constant Quad
            }
        }
    }
}

}

The material inspector is inadequate for this, though; an EditorWindow is usable:

using UnityEngine;
using UnityEditor;

class SoftEdgePlusCutoffWindow : EditorWindow {

static SoftEdgePlusCutoffWindow window;
static Material material;

[MenuItem("Assets/Adjust Soft Edge + Cutoff", true)] static bool Validate () {
    if (window) return false;

    try {material = (Selection.activeObject as GameObject).renderer.sharedMaterial;}
    catch {material = Selection.activeObject as Material;}
    return material ? material.HasProperty("_CutoffInverseQuarter") : false;
}

[MenuItem ("Assets/Adjust Soft Edge + Cutoff", false, 2000)] static void Open () {
    window = GetWindow<SoftEdgePlusCutoffWindow>(true, material.name);
    window.autoRepaintOnSceneChange = true;
}

// The alpha channel of the texture needs to be scaled so that that it is white at the cutoff value.
// That way, there will always be a full invisible-opaque transition,
// instead of there being a visible alpha tested edge with lower cutoff values.
// You can only make the alpha 4x as bright, with a fixed function shader, 
// hence the .25 here, and Quad in the shader. 
bool listeningForGuiChanges;
void OnGUI () {
    Event currentEvent = Event.current;
    if (currentEvent.type == EventType.MouseDown && currentEvent.button == 0) {
        Undo.SetSnapshotTarget(material, material.name + " Cutoff Adjustment");
        Undo.CreateSnapshot();
        Undo.ClearSnapshotTarget();
        listeningForGuiChanges = true;
    }

    material.SetFloat("_Cutoff", EditorGUILayout.Slider("Cutoff", material.GetFloat("_Cutoff"), .25F, 1));
    material.SetFloat("_CutoffInverseQuarter", .25F / material.GetFloat("_Cutoff"));

    if (listeningForGuiChanges && GUI.changed) {
        Undo.SetSnapshotTarget(material, material.name + " Cutoff Adjustment");
        Undo.RegisterSnapshot();
        listeningForGuiChanges = false;     
    }   
}

}

This works on iOS. Please let us know what happens on Android.

[LoungeKatt]

In case anyone stumbles across this like I did, Android has issues with AlphaTest and clip(), which can be resolved by editing the shader above to read:

Shader "Transparent/Cutout/Soft Edge Unlit +" {
 
Properties {
    _MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
    _Cutoff ("Base Alpha cutoff  (Use Script)", Float) = 1
    _CutoffInverseQuarter ("Cutoff inverse / 4  (Use Script)", Float) = 1
}
 
Category {
    Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="TransparentCutout"}
 
    SubShader {
        Pass {
            GLSLPROGRAM
            varying mediump vec2 uv;
 
            #ifdef VERTEX
            void main() {
                gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
                uv = gl_MultiTexCoord0.xy;
            }
            #endif
 
            #ifdef FRAGMENT
            uniform lowp sampler2D _MainTex;
            uniform lowp float _Cutoff;
            void main() {
                vec4 texture = texture2D(_MainTex, uv);
                if (texture.a < _Cutoff) discard;
                gl_FragColor = texture;
            }
            #endif      
            ENDGLSL
        }
        Pass {
            ZTest Less  ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha
 
            GLSLPROGRAM
            varying mediump vec2 uv;
 
            #ifdef VERTEX
            void main() {
                gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
                uv = gl_MultiTexCoord0.xy;
            }
            #endif
 
            #ifdef FRAGMENT
            uniform lowp sampler2D _MainTex;
            uniform lowp float _Cutoff;
            void main() {
                vec4 texture = texture2D(_MainTex, uv);
                gl_FragColor = vec4(texture.rgb, texture.a / _Cutoff);
            }
            #endif      
            ENDGLSL
        }   
    }
 
    SubShader {
        Pass {
            ZTest Less  ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha
            SetTexture[_MainTex] {
                ConstantColor(0,0,0, [_CutoffInverseQuarter])
                Combine texture, texture * constant Quad
            }
        }
    }
}
 
}