CGPROGRAM

        // Physically based Standard lighting model, and enable shadows on all light types

        #pragma surface surf Standard fullforwardshadows vertex:vert

struct Input {

            float2 uv_MainTex;

            float3 worldPos;

            float4 modelPos_;

        };

void vert(inout appdata_full v, out Input o)

        {

            UNITY_INITIALIZE_OUTPUT(Input, o);

            o.modelPos_ = v.vertex;

        }

        ENDCG

float lat = degrees(acos(IN.modelPos_.y / _R));//[0,180]