   mesh in .x file
  I found there is a mesh normal  in  mesh {..} in x. file normal is composed by 3 float.see below   MeshNormals  {    667;    0.000000;-0.994176;-0.107770;,    -0.038280;-0.996654;-0.072217;,    0.571241;-0.799374;-0.186240;,    0.633843;-0.714976;-0.295046;,    0.660265;-0.705742;-0.256861;,.......    -0.998319;0.028576;0.050426;,    -0.998373;0.028578;0.049341;;    487;    3;0,1,0;,  // Question : what is these four int value represent???????    3;2,3,4;,    3;3,5,4;,    3;6,7,8;,    3;7,9,8;,    3;10,11,12;,    3;13,14,15;,    3;16,17,18;,    3;19,20,21;,    3;22,19,21;,    3;23,19,24;,    3;19,25,20;,    3;20,25,26;,.........................   }
  Check the X file reference in the documentation: DirectX Graphics->Reference->X File reference (legacy)->X File format reference->X File templates.This is the MeshNormals template:template MeshNormals{    < F6F23F43-7686-11cf-8F52-0040333594A3 >    DWORD nNormals;    array Vector normals[nNormals];    DWORD nFaceNormals;    array MeshFace faceNormals[nFaceNormals];} As you can see, 667 is the number of normals, followed by the normals. 487 is the number of face normals, followed by a number of 'MeshFace's.template MeshFace{    < 3D82AB5F-62DA-11cf-AB39-0020AF71E433 >    DWORD nFaceVertexIndices;    array DWORD faceVertexIndices[nFaceVertexIndices];} So, the '3' is the number of vertices composing the face. Followed by 3 indices into the mesh vertices, defining the face itself.   