Vertex Buffer overrun

Graphics and GPU Programming Programming

Started by lucky6969b June 16, 2015 12:44 PM

2 comments, last by Matias Goldberg 8 years, 10 months ago

lucky6969b

1,334

Author

June 16, 2015 12:44 PM

Does anyone have an idea why the vertex buffer would overrun? Thanks Jack


// load vertex into m_verts
    LPDIRECT3DVERTEXBUFFER9 pVBuf;
    if (SUCCEEDED(m_pMesh->GetVertexBuffer(&pVBuf))) {
        CUSTOMVERTEX *pVert;
        if (SUCCEEDED(pVBuf->Lock(0, 0, (LPVOID *)&pVert, D3DLOCK_DISCARD))) {
            DWORD numVerts = m_pMesh->GetNumVertices();
            for (int i = 0; i<numVerts; i++) {                
                float x = pVert[i].x;
                float y = pVert[i].y;
                float z = pVert[i].z;
                pVert++;
                addVertex(x, y, z, vcap);
                
            }
            pVBuf->Unlock();
        }
        pVBuf->Release();
    }

Mona2000

1,967

June 16, 2015 02:14 PM

I don't know if that's the only issue, but locking a buffer with D3DLOCK_DISCARD and then reading from it is not a valid operation.

snake5

1,589

June 16, 2015 02:28 PM

Many possible reasons, vertex buffer might be too small, there might be a different vertex format.

But most likely... you're incrementing your offset twice - once on "i++" and the second time on "pVert++;". Either remove the second one or treat pVert as the pointer to current vertex ("pVert.x" -> "pVert->x" etc.)

I don't know if that's the only issue, but locking a buffer with D3DLOCK_DISCARD and then reading from it is not a valid operation.

Fun fact: It actually was valid in Windows XP and some games relied on the flag doing nothing (and then they broke on Vista/7/8 and I had to make a proxy DLL to play them).

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Matias Goldberg

9,637

June 16, 2015 04:10 PM

There's a lot of information missing.

sizeof(CUSTOMVERTEX) could be wrong.

The vertex buffer could be smaller than sizeof(CUSTOMVERTEX) * numVerts;

Also whatever happens inside addVertex could be causing stack corruption. A lot of unknown variables to say.

I don't know if that's the only issue, but locking a buffer with D3DLOCK_DISCARD and then reading from it is not a valid operation.

Fun fact: It actually was valid in Windows XP and some games relied on the flag doing nothing (and then they broke on Vista/7/8 and I had to make a proxy DLL to play them).

It was invalid then, still invalid now. It "just worked" doesn't mean it was valid. Many games violate the API rules.

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Vertex Buffer overrun

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