Read Vertices from a mesh

[compiler 122]

Hi, i wanna read vertices from a mesh. the problem is: i dont know the format of the vertices. I tried to read the vertex format from the mesh and pass the type via the GetType method to the lockvertex buffer method:

VertexFormats meshVertexFormat = mesh.VertexFormat;
Array verts = mesh.LockVertexBuffer(meshVertexFormat.GetType(), LockFlags.None, mesh.NumberVertices);

but if i execute this code ill get an unhandled exception of type 'System.ArgumentException': Additional information: Object contains non-primitive or non-blittable data. and even if this would work i still wouldnt know how to cast verts to the appropriate array type. so i need something like this (which doesnt compile in this form):

Type t = mesh.VertexFormat.GetType();
t[] verts = (t[])mesh.LockVertexBuffer(t, LockFlags.None, mesh.NumberVertices);

anybody knows how to get the vertices? (maybe with some kind of reflection?)

[TheMaskedFace 122]

In fact you do not really know the format of vertices of your mesh.you can use DirectX's CustomVertex type, but also you can implement your own custom vertex type.

CustomVertex.PositionNormalTextured[] modelVertices;

modelVertices = (CustomVertex.PositionNormalTextured[])mesh.VertexBuffer.Lock(/*_VERTEXSTART_*/, typeof(CustomVertex.PositionNormalTextured), LockFlags.ReadOnly, /*_VERTEXCOUNT_*/);
                vertexBuffers = new VertexBuffer(typeof(CustomVertex.PositionNormalTextured), /*_VERTEXCOUNT_*/, device, Usage.WriteOnly, CustomVertex.PositionNormalTextured.Format, Pool.Default);
                vertexBuffers.SetData(modelVertices, 0, LockFlags.None);

The concept is like that.Maybe this snippet helps you

[compiler 122]

i guess u didnt understand me. i DONT know which vertex format the mesh has so i cant just use CustomVertex.PositionNormalTextured. It also could be PositionOnly or anything else. Did nobody ever had this problem? ;(

[jollyjeffers 1570]

I've done this sort of thing before, but I've not done it via MDX...

There are two approaches:

1. Identify the format (in Native DX you can extract the FVF/declaration and work backwards) and then try and match it up to an appropriate format. This makes for slightly clunky code and you can only accept a pre-determined number of formats.

2. Identify the components you are actually interested in extracting (e.g. if you only want the diffuse colour or the tex coords) and construct a vertex structure that matches the desired output. Then determine if the mesh's format is a superset of your desired output (e.g. it contains as much or more information), if it's not then the call fails - the input mesh doesn't have the appropriate data. Otherwise, clone the mesh to a temporary instance with your desired format. You now know the vertex format of the temporary mesh and can extract as you wish.

The second one is a little more involved, but is pretty robust..

hth
Jack

[DonnieDarko 251]

The UVAtlas SDK sample contains the CD3DXCrackDecl class which simplifies reading and writing arbitrary vertex components. Here's some sample code reading vertex positions from ID3DXMesh:

void *pVertexData;
hr = mesh->LockVertexBuffer(D3DLOCK_NOSYSLOCK, &pVertexData);
D3DVERTEXELEMENT9 decl[MAX_FVF_DECL_SIZE];
hr = mesh->GetDeclaration(decl);
CD3DXCrackDecl cd;
cd.SetDeclaration(decl);
cd.SetStreamSource(0, pVertexData, 0);

D3DXVECTOR3 pos;
int vertexIndex = 0;
cd.DecodeSemantic(D3DDECLUSAGE_POSITION, 0, vertexIndex, (float*)&pos, 3);

It's not managed, but maybe the CD3DXCrackDecl class can be of some help to you.