shaderで新しいnormalを計算する

float3 getNewVertPos(float3 pos){
                
            float4 hoge = float4(0,0,0,0);
            hoge.y = _Amp+_Amp*sin( 
                (pos.x*_Detail.x+pos.z*_Detail.z) *3.1415 + _Time.y*4
            );
            hoge.y *= step(0,pos.y);//マイナスyは無効化する
            return pos + hoge;

        }

        float3 getNewNormal(float3 pos, float3 normal, float3 tangent){
            float3 vertPosition = getNewVertPos( pos );

            // calculate the bitangent (sometimes called binormal) from the cross product of the normal and the tangent
            float3 bitangent = cross( normal, tangent );

            // how far we want to offset our vert position to calculate the new normal
            float vertOffset = 0.01;

            float3 v1 = getNewVertPos( pos + tangent * vertOffset );
            float3 v2 = getNewVertPos( pos + bitangent * vertOffset );

            // now we can create new tangents and bitangents based on the deformed positions
            float3 newTangent = v1 - vertPosition;
            float3 newBitangent = v2 - vertPosition;
            
            float3 outNormal = cross(newTangent,newBitangent);

            return outNormal;
        }