Custom shader doesn't receive shadow

hi !

i have got a problem receiving shadows with this shader.

Code (CSharp):

1. Shader "Custom/TerrainSand"
2. {
3.     Properties
4.     {
5.         _Color("Main Color", Color) = (1,1,1,0.5)
6.         _MainTex("Base (RGB)", 2D) = "white" {}
7.         _MainTex2("Base 2 (RGB)", 2D) = "white" {}
8.         _Mask("Mix Mask (A)", 2D) = "gray" {}
9.         _BumpMap("Bumpmap (RGB)", 2D) = "bump" {}
10.     }
11.  
12.     Category
13.     {
14.         /* Upgrade NOTE: commented out, possibly part of old style per-pixel lighting: Blend AppSrcAdd AppDstAdd */
15.         Fog{ Color[_AddFog] }
16.  
17.         // ------------------------------------------------------------------
18.         // ARB fragment program
19.  
20.         #warning Upgrade NOTE: SubShader commented out; uses Unity 2.x per-pixel lighting. You should rewrite shader into a Surface Shader.
21.         SubShader
22.         {
23.         // Ambient pass
24.         Pass{
25.             Tags{ "LightMode" = "Always" /* Upgrade NOTE: changed from PixelOrNone to Always */ }
26.             Color[_PPLAmbient]
27.             SetTexture[_MainTex]{ combine texture }
28.             SetTexture[_Mask]{ combine previous, texture }
29.             SetTexture[_MainTex2]{ combine texture lerp(previous) previous }
30.             SetTexture[_MainTex2]{ constantColor[_Color] combine previous * primary DOUBLE, previous * constant }
31.         }
32.  
33.     // Vertex lights
34.         Pass
35.         {
36.             Tags{ "LightMode" = "ForwardBase" }
37.             Lighting On
38.             Material{
39.             Diffuse[_Color]
40.             Emission[_PPLAmbient]
41.         }
42.  
43.         SetTexture[_MainTex]{ combine texture }
44.         SetTexture[_Mask]{ combine previous, texture }
45.         SetTexture[_MainTex2]{ combine texture lerp(previous) previous }
46.         SetTexture[_MainTex2]{ constantColor[_Color] combine previous * primary DOUBLE, previous * constant }
47.     }
48.  
49.     // Pixel lights
50.     Pass
51.     {
52.         Name "PPL"
53.         Tags{ "LightMode" = "Pixel" }
54.  
55.         CGPROGRAM
56.         // Upgrade NOTE: excluded shader from DX11; has structs without semantics (struct v2f members uv,lightDirT)
57.         #pragma exclude_renderers d3d11
58.         #pragma vertex vert
59.         #pragma fragment frag
60.         #pragma fragmentoption ARB_fog_exp2
61.         #pragma fragmentoption ARB_precision_hint_fastest
62.         #pragma multi_compile_builtin
63.  
64.         #include "UnityCG.cginc"
65.         #include "AutoLight.cginc"
66.  
67.         struct v2f
68.         {
69.             float4 pos : SV_POSITION;
70.             LIGHTING_COORDS()
71.             float2  uv[4];
72.             float3  lightDirT;
73.  
74.         };
75.  
76.         float4 _MainTex_ST, _MainTex2_ST, _Mask_ST, _BumpMap_ST;
77.  
78.         v2f vert(appdata_tan v)
79.         {
80.             v2f o;
81.             o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
82.             o.uv[0] = TRANSFORM_TEX(v.texcoord, _MainTex);
83.             o.uv[1] = TRANSFORM_TEX(v.texcoord, _MainTex2);
84.             o.uv[2] = TRANSFORM_TEX(v.texcoord, _Mask);
85.             o.uv[3] = TRANSFORM_TEX(v.texcoord, _BumpMap);
86.  
87.             TANGENT_SPACE_ROTATION;
88.             o.lightDirT = mul(rotation, ObjSpaceLightDir(v.vertex));
89.  
90.             TRANSFER_VERTEX_TO_FRAGMENT(o);
91.             return o;
92.         }
93.  
94.         uniform sampler2D _MainTex;
95.         uniform sampler2D _MainTex2;
96.         uniform sampler2D _Mask;
97.         uniform sampler2D _BumpMap;
98.  
99.         float4 frag(v2f i) : COLOR
100.         {
101.             half4 col1 = tex2D(_MainTex,i.uv[0]);
102.             half4 col2 = tex2D(_MainTex2,i.uv[1]);
103.             half mix = tex2D(_Mask,i.uv[2]).a;
104.             half4 texcol = lerp(col1,col2,mix);
105.  
106.             // get normal from the normal map
107.             float3 normal = tex2D(_BumpMap, i.uv[3]).xyz * 2 - 1;
108.             float atten = LIGHT_ATTENUATION(i);
109.             return DiffuseLight(i.lightDirT, normal, texcol, atten);
110.         }
111.  
112.         ENDCG
113.         }
114.     }
115.  
116.     // ------------------------------------------------------------------
117.     // Four texture cards
118.  
119.     SubShader
120.     {
121.         // Vertex lit
122.         Pass
123.         {
124.             Lighting On
125.             Material
126.             {
127.                 Diffuse[_Color]
128.                 Ambient[_Color]
129.             }
130.  
131.             SetTexture[_MainTex]{ combine texture }
132.             SetTexture[_Mask]{ combine previous, texture }
133.             SetTexture[_MainTex2]{ combine texture lerp(previous) previous }
134.             SetTexture[_MainTex2]{ constantColor[_Color] combine previous * primary DOUBLE, previous * constant }
135.             }
136.         }
137.     }
138.     FallBack "Diffuse"
139. }

It does what i need (2 texture on terrain with a mask) but i can't figure out why there is no shadows...

Can anyone point me to the right direction to solve this problem?

Thanks for your help and sorry for the "n+1" post about this