這東西好難找LIGHT_ATTENUATION(a)

shadow 的結果就在這個衰減裏，這誰能猜的著，我一點點測出來的，reference也很難找

感謝這位http://blog.csdn.net/candycat1992/article/details/42460959

1. #ifdef POINT
2. #define LIGHTING_COORDS(idx1,idx2) float3 _LightCoord : TEXCOORD##idx1; SHADOW_COORDS(idx2)
3. uniform sampler2D _LightTexture0;
4. uniform float4x4 _LightMatrix0;
5. #define TRANSFER_VERTEX_TO_FRAGMENT(a) a._LightCoord = mul(_LightMatrix0, mul(_Object2World, v.vertex)).xyz; TRANSFER_SHADOW(a)
6. #define LIGHT_ATTENUATION(a) (tex2D(_LightTexture0, dot(a._LightCoord,a._LightCoord).rr).UNITY_ATTEN_CHANNEL * SHADOW_ATTENUATION(a))
7. #endif
9. #ifdef DIRECTIONAL
10. #define LIGHTING_COORDS(idx1,idx2) SHADOW_COORDS(idx1)
11. #define TRANSFER_VERTEX_TO_FRAGMENT(a) TRANSFER_SHADOW(a)
12. #define LIGHT_ATTENUATION(a) SHADOW_ATTENUATION(a)
13. #endif

unity shadow