Glow/Spotlight shader reacting different cross-platform

Hi,

I’m working on a project where we use a shader that creates a spotlight/cameralight effect. This effect doesn’t seem to work on OSX/Android/iOS and I can’t seem to find the reason for that, but it’s probably something with OpenGL. The rest of the shader works fine but the spotlight/glow effect reacts way different on Mac.

Could someone please help me on this issue. Pictures and code are posted below.

Shader "Custom/GlowLine" {
 Properties {
     _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
     _MainTex ("Particle Texture", 2D) = "white" {}
     _BrightnessFactor ("Brightness Factor", Float ) = 1.0
     _BrightnessHardness( "Brightness Hardness", Float ) = 2.0
     _LineHardness( "Line Hardness", Float ) = 2.0
 }
 
 Category {
     Tags { "Queue"="Overlay" "IgnoreProjector"="True" "RenderType"="Transparent" }
     Blend SrcAlpha One
     ZTest Always
     AlphaTest Greater .01
     ColorMask RGB
     Cull Back Lighting Off ZWrite On Fog { Color (0,0,0,0) }
     BindChannels {
         Bind "Color", color
         Bind "Vertex", vertex
         Bind "TexCoord", texcoord
     }
     
     // ---- Fragment program cards
     SubShader {
         Pass {
         
             CGPROGRAM
             #pragma exclude_renderers xbox360
             #pragma vertex vert
             #pragma fragment frag
             #pragma fragmentoption ARB_precision_hint_fastest
             #pragma multi_compile_particles
 
             #include "UnityCG.cginc"
 
             sampler2D _MainTex;
             fixed4 _TintColor;
             float _BrightnessFactor;
             float _BrightnessHardness;
             float _LineHardness;
             
             struct appdata_t {
                 float4 vertex : POSITION;
                 fixed4 color : COLOR;
                 float2 texcoord : TEXCOORD0;
             };
 
             struct v2f {
                 float4 vertex : POSITION;
                 fixed4 color : COLOR;
                 float2 texcoord : TEXCOORD0;
                 float4 position : TEXCOORD1;
             };
             
             float4 _MainTex_ST;
 
             v2f vert( appdata_t v )
             {
                 v2f o;
                 o.vertex = mul( UNITY_MATRIX_MVP, v.vertex );
                 o.color = v.color;
                 o.texcoord = TRANSFORM_TEX( v.texcoord,_MainTex );
                 o.position = o.vertex;
                 return o;
             }
 
             sampler2D _CameraDepthTexture;
             
             fixed4 frag( v2f IN ) : COLOR
             {
                 half4 texColor = pow(tex2D( _MainTex, IN.texcoord ), _LineHardness );
                 float brightness = 1.0f / pow(dot( IN.position, IN.position ), _BrightnessHardness) * texColor.a;
                 return 2.0f * (IN.color )* _TintColor * texColor + (brightness * _BrightnessFactor) * 0.1f;
             }
             ENDCG 
         }
     }     
     
     // ---- Dual texture cards
     SubShader {
         Pass {
             SetTexture [_MainTex] {
                 constantColor [_TintColor]
                 combine constant * primary
             }
             SetTexture [_MainTex] {
                 combine texture * previous DOUBLE
             }
         }
     }
     
     // ---- Single texture cards (does not do color tint)
     SubShader {
         Pass {
             SetTexture [_MainTex] {
                 combine texture * primary
             }
         }
     }
 }
 }

I found the solution:

On Windows (with D3D9/D3D11) a certain formula returns a different number than with other compilers.

I added this to make it work:

fixed4 frag( v2f IN ) : COLOR
{
	half4 texColor = pow(tex2D( _MainTex, IN.texcoord ), _LineHardness );
	float brightness = 1.0f / pow(dot( IN.position, IN.position ), _BrightnessHardness) * texColor.a;
	float osFactor = 0.9f;
	#if SHADER_API_D3D9 || SHADER_API_D3D11
	osFactor = 0.1f;
	#endif
    return 2.0f * (IN.color )* _TintColor * texColor + (brightness * _BrightnessFactor) * osFactor;
}

osFactor (OS specific factor) was 0.1, but seems to act the same on OSX and Linux with 1 minus 0.1.

Hope this info will help others with the same problem!