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## Retriving Indices from mesh buffer

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### #1NoahV  Members

Posted 07 January 2013 - 10:51 AM

So I'm using ID3DXMESH to store a .X file, I'm loading it into the application with D3DXLoadMeshHierarchyFromX. I'm trying to get the vertex and index buffer from the mesh but getting incorrect results. The vertex buffer is correct but the index buffer is not, at least I don't think so. To simplify things; I created a basic cube mesh .X file. I've been changing around the index values of the file and the model changes shape but the returned index buffer does not reflect what is stated in the file.

DWORD numFaces = pCurrentFrame->pMeshContainer->MeshData.pMesh->GetNumFaces();

if(MESHFLAGS&D3DXMESH_32BIT)
{
DWORD* indices;
DWORD tempIndex;

for(DWORD k = 0; k < (numFaces*3); k++)
{
memcpy(&tempIndex, indices, sizeof(DWORD));
indices++;
}
}

else
{
WORD* indices;
WORD tempIndex;

for(DWORD k = 0; k < (numFaces*3); k++)
{
memcpy(&tempIndex, indices, sizeof(WORD));
tempIndex = 0;
indices++;
}
}

pCurrentFrame->pMeshContainer->MeshData.pMesh->UnlockIndexBuffer();

what I get back for my index values is 0,1,2,3,4,5,6,7,8,9,10,6,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,23,28,29,30,31,28,32

here's the vertex and index information from the file.

Mesh { //Cube_001 Mesh
36;
-1.000000; 1.000000;-1.000000;,
1.000000; 1.000000;-1.000000;,
1.000000; 0.999999; 1.000000;,
-1.000000; 1.000000; 1.000000;,
-1.000000; 1.000000;-1.000000;,
1.000000; 0.999999; 1.000000;,
-1.000000; 1.000000; 1.000000;,
-1.000000;-1.000000; 1.000000;,
-1.000000;-1.000000;-1.000000;,
-1.000000; 1.000000;-1.000000;,
-1.000000; 1.000000; 1.000000;,
-1.000000;-1.000000;-1.000000;,
-1.000000;-1.000000;-1.000000;,
0.999999;-1.000001; 1.000000;,
1.000000;-1.000000;-1.000000;,
-1.000000;-1.000000;-1.000000;,
-1.000000;-1.000000; 1.000000;,
0.999999;-1.000001; 1.000000;,
1.000000;-1.000000;-1.000000;,
1.000000; 0.999999; 1.000000;,
1.000000; 1.000000;-1.000000;,
1.000000;-1.000000;-1.000000;,
0.999999;-1.000001; 1.000000;,
1.000000; 0.999999; 1.000000;,
0.999999;-1.000001; 1.000000;,
-1.000000; 1.000000; 1.000000;,
1.000000; 0.999999; 1.000000;,
0.999999;-1.000001; 1.000000;,
-1.000000;-1.000000; 1.000000;,
-1.000000; 1.000000; 1.000000;,
-1.000000;-1.000000;-1.000000;,
1.000000;-1.000000;-1.000000;,
1.000000; 1.000000;-1.000000;,
-1.000000; 1.000000;-1.000000;,
-1.000000;-1.000000;-1.000000;,
1.000000; 1.000000;-1.000000;;
12;
3;0;1;2;,
3;1;4;5;,
3;6;7;9;,
3;9;10;11;,
3;3;1;4;,
3;15;16;12;,
3;18;14;20;,
3;21;22;23;,
3;24;25;27;,
3;27;35;29;,
3;30;31;32;,
3;33;34;35;;

It doesn't seem like it's right, is the LoadHierarchy function doing some kind of optimization behind the scenes, are the returned values somehow correct or am I just doing something wrong?

Thanks for any help!

### #2Anddos  Members

Posted 07 January 2013 - 11:59 AM

This is how i lock the mesh and get the vertices , you might be able to work something out with the indices


</p><div>void LockMesh(LPD3DXMESH Mesh)</div>
<div>{</div>
<div> </div>
<div> </div>
<div>BYTE* lpbVb;</div>
<div>int numIndices;</div>
<div>BYTE *lpIB;</div>
<div>DWORD idxVbVert0, idxVbVert1, idxVbVert2;</div>
<div>D3DINDEXBUFFER_DESC ibdesc;</div>
<div>    LPDIRECT3DINDEXBUFFER9 lpIndexBuffer = NULL;</div>
<div>Mesh->GetIndexBuffer( &lpIndexBuffer );</div>
<div>lpIndexBuffer->GetDesc( &ibdesc );</div>
<div>if(ibdesc.Format == D3DFMT_INDEX32)</div>
<div>{</div>
<div>//MessageBox(NULL,"ibdesc.Format 32","",0);</div>
<div>numIndices = ibdesc.Size / sizeof(DWORD);</div>
<div>}</div>
<div>else</div>
<div>{</div>
<div>//MessageBox(NULL,"ibdesc.Format 16","",0);</div>
<div>numIndices = ibdesc.Size / sizeof(WORD);</div>
<div>}</div>
<div> </div>
<div>DWORD numBytesPerVertex = Mesh->GetNumBytesPerVertex();</div>
<div> </div>
<div> </div>
<div>for(int i=0; i<numIndices; i += 3 )</div>
<div>{</div>
<div>idxVbVert0 = ((WORD*)lpIB)[ i ];</div>
<div>idxVbVert1 = ((WORD*)lpIB)[ i+1 ];</div>
<div>idxVbVert2 = ((WORD*)lpIB)[ i+2 ];</div>
<div> </div>
<div>D3DXVECTOR3 v0 = *(D3DXVECTOR3*) &lpbVb[ idxVbVert0 * numBytesPerVertex ];</div>
<div>   D3DXVECTOR3 v1 = *(D3DXVECTOR3*) &lpbVb[ idxVbVert1 * numBytesPerVertex ];</div>
<div>D3DXVECTOR3 v2 = *(D3DXVECTOR3*) &lpbVb[ idxVbVert2 * numBytesPerVertex ];</div>
<div> </div>
<div>}</div>
<div> </div>
<div>Mesh->UnlockVertexBuffer();</div>
<div>Mesh->UnlockVertexBuffer();</div>
<div>}</div>
<div>

### #3NoahV  Members

Posted 07 January 2013 - 06:28 PM

Thanks for the response! I made some changes based on your code example. Unfortunately same results

### #4NoahV  Members

Posted 09 January 2013 - 09:39 AM

Ok so if anyone is interested in how this all worked out. I took the time to remove the duplicate vertices in the .X cube file so that there are now only 8 vertices, which is correct for an indexed cube. Vertex and index values are now listed below. The index buffer now returns different values, still not the ones listed in the file though. I took a look at the vertex buffer in the application and the vertices have been reordered, also for some reason GetNumVertices() returns 16 instead of eight. It's obvious that each of the 8 vertices has been duplicated in the buffer, I have no idea why. Anyway I matched the vertices in the vertex buffer to the vertices in the file. Then I matched the returned indices to those values, and the 12 faces in the index buffer are indeed correct and identical to the 12 faces in the .X file. So bottom line is that D3DXLoadHierarchyFromX() is doing some things to both the vertex and index buffers behind the scenes, but adding an additional 8 vertices certainly does not seem like an optimization. Oh well at least I know the indices are right now, I'm going to try to do a vertex cache mesh->OptimizeInPlace and see if that removes the duplicate vertices. If that doesn't work I guess I'll just add some code to remove the duplicate vertices.

Mesh { //Cube_001 Mesh
8;
-1.000000; 1.000000;-1.000000;,
1.000000; 1.000000;-1.000000;,
-1.000000;-0.999999;-1.000000;,
1.000000;-1.000000;-1.000000;,
-1.000000; 1.000000; 1.000000;,
1.000000; 1.000000; 1.000000;,
-1.000000;-0.999999; 1.000000;,
1.000000;-1.000000; 1.000000;;
12;
3;0;1;2;,
3;2;1;3;,
3;5;4;6;,
3;6;7;5;,
3;1;5;3;,
3;3;5;7;,
3;4;0;2;,
3;6;0;2;,
3;0;4;1;,
3;4;5;1;,
3;2;3;6;,
3;6;3;7;;

### #5NoahV  Members

Posted 10 January 2013 - 09:43 AM

Ok last bit of info. I thought the vertex buffer contained duplicate vertices. My .X file lists only 8 vertices but the application says 16 vertices. I wasn't bothering to look at the indexed normal list contained in the .X file. D3DXLoadHierarchyFromX is creating vertices with the same position, but with different normals, so they are not duplicates and everything seems to be working as intended.

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