Unity Shader 获取模型空间坐标

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]