Position of fields (position, normal, etc.) in a D3D9 vertex

Question

Hello,

I'm trying to read 3D models which were created for a DirectX applications, which are defined in the following way :

• In the file header, the Flexible Vertex Format (FVF) of the mesh is given (actually, I have any combinations of D3DFVF_{XYZ,DIFFUSE,NORMAL,TEX1,TEX2} in the meshes I tested)
• Then, n vertices are given in a linear pattern, with the fields presents according to the FVF.

However, I do not know the order of these fields. The logic would be that it is defined somewhere in DirectX documentation, but I was unable to find it. For example, which of these two structures is correct with FVF = D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_NORMAL (C syntax, but this problem applies to every language) ?

// This one ?
struct vertex1
{
    D3DVERTEX pos;
    DWORD color;
    D3DVERTEX normal;
};

// Or this one ?
struct vertex2
{
    D3DVERTEX pos;
    D3DVERTEX normal;
    DWORD color;
};

I would like a general answer to this question with all the possible fields (for example, XYZ before DIFFUSE before NORMAL before TEX1 before TEX2). A pointer to the right page of the documentation would be fine too as I was not able to find it :) .

Answer 1

Well you should be defining it as follows.

struct EitherVertex
{
    float x, y, z;
    DWORD col;
    float nx, ny, nz
};

or

struct EitherVertex
{
    D3DXVECTOR3 pos;
    DWORD col;
    D3DXVECTOR3 nrm;
};

(D3DVERTEX refers to an entire vertex struct and not just a 3 element vector)

Of your 2 options a lot depends on how you access those vert elements. If you are using the depreceated FVF then the second of your 2 choice is the more correct.

If however you are using Vertex Declarations then YOU define where in the struct the relevant data is and the ordering does not matter.

Answer 2

here you are

FVF (OP says the information on this page is incorrect. I dont know, didnt check if FVF positioning is correct)

Generator