MatCap shader imitation of blender 2.8s matcap

Hello I'm trying to make a blender2.8 matcap imitation so far its fairly good , the error is in the corners (hopefully i have the image attached correctly , black with white edges) , i don't really know how to fix my mistake the idea is to use a dot product on a surface to eye vector with a tangent of the normals.
thanks.

Code (CSharp):

1. Shader "Unlit/matcatallsurface_vf"
2. {
3.     Properties
4.     {
5.         _MainTex ("Texture", 2D) = "white" {}
6.         _MatCap ("matcap",2D) = "black" {}
7.     }
8.     SubShader
9.     {
10.         Tags { "RenderType"="Opaque" }
11.         LOD 100
12.  
13.         Pass
14.         {
15.         Tags { "LightMode" = "Always" }
16.             CGPROGRAM
17.             #pragma vertex vert
18.             #pragma fragment frag
19.            
20.  
21.             #include "UnityCG.cginc"
22.  
23.             struct appdata
24.             {
25.                 float4 vertex : POSITION;
26.                 float2 uv : TEXCOORD0;
27.                 float3 normal : NORMAL;
28.        
29.             };
30.  
31.             struct v2f
32.             {
33.                 float2 uv : TEXCOORD0;
34.                 UNITY_FOG_COORDS(1)
35.                 float4 vertex : SV_POSITION;
36.                 float2 mat : TEXCOORD1;
37.                
38.             };
39.  
40.             sampler2D _MainTex , _MatCap;
41.             float4 _MainTex_ST;
42.            
43.             v2f vert (appdata v)
44.             {
45.                 v2f o;
46.  
47.                 float3 worldPos = mul(unity_ObjectToWorld, v.vertex);
48.                 float3 worldNormal = mul(unity_ObjectToWorld, v.normal);
49.                 float3 toCam = normalize(_WorldSpaceCameraPos.xyz - worldPos);
50.  
51.                 float3 cx = normalize( cross(-worldNormal, UNITY_MATRIX_V[1]) );
52.                 float3 cy = normalize( cross(-worldNormal, UNITY_MATRIX_V[0]) );
53.  
54.                 o.mat = float2( dot(toCam, cx) , dot(toCam, -cy) )*.5+.5;
55.  
56.                 o.vertex = UnityObjectToClipPos(v.vertex);
57.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
58.            
59.                 return o;
60.             }
61.            
62.             fixed4 frag (v2f i) : SV_Target
63.             {
64.                
65.                 fixed4 col = tex2D(_MainTex, i.uv);
66.                 fixed4 matcap = tex2D(_MatCap, i.mat.xy);
67.                 return col *2*matcap;
68.             }
69.             ENDCG
70.         }
71.     }
72. }

 

Ok my main problem seems to be in normalizing the cross product instead of getting something like (1,1) getting (.7,.7) for a length of 1,the above code has mat removed form appdata by accident trying to clean up post .
the odd problem now is serious curvature when looking at a similar surfaces of the viewing angle.