   Question about relief mapping
  Hi, I am reading the article "Real-time relief mapping on arbitrary polygonal surfaces" by  F Policarpo 2005, you can get the article by the link bellowhttp://www.inf.ufrgs.br/~oliveira/pubs_files/Policarpo_Oliveira_Comba_RTRM_I3D_2005.pdf I have several questions about this article, all of them is about math. Question 1:Why calculate the view vector in tangent space and size of search in texture space like this?(you can find the hlsl code at the end of the article)// view vector in tangent spaces = normalize(float3(dot(v,IN.tangent.xyz),dot(v,IN.binormal.xyz),dot(IN.normal,-v)));// size and start position of search in texture spaceds = s.xy*depth/s.z;dp = IN.texcoord*tile;Thanks in advance.   