HRESULT CTerrain::FillVB( LPDIRECT3DDEVICE8 pd3dDevice )
{
	if( pd3dDevice == NULL )
		return E_FAIL;
	
	// create the vertices

	DWORD count = 0L;
	
	for ( float x = 0; x < m_nWidth; x ++ )
	{
		for ( float z = 0; z < m_nHeight; z ++ )
		{
			m_pMapIndex[count].p.x = x*2;
			m_pMapIndex[count].p.y = GetCell( x, z );
			m_pMapIndex[count].p.z = z*2;
			m_pMapIndex[count].tu0 = ((x)/m_nWidth);
			m_pMapIndex[count].tv0 = 1.0f-((z)/m_nHeight);
			count++;

		}
	}

	if( FAILED( pd3dDevice->CreateVertexBuffer(m_dwNumVerts * sizeof(TERRAIN_VERT),
												  0, D3DFVF_TERRAIN,
												  D3DPOOL_DEFAULT, &m_pVB ) ) )
	{
		return E_FAIL;
	}
	
	// Fill vertex buffer

	VOID* pVertices;
	if( FAILED( m_pVB->Lock( 0, sizeof(TERRAIN_VERT) * m_dwNumVerts, (BYTE**)&pVertices, 0 ) ) )
	{
		return E_FAIL;
	}
	memcpy(pVertices, m_pMapIndex, sizeof(TERRAIN_VERT) * m_dwNumVerts);
	m_pVB->Unlock();

	return S_OK;

}

HRESULT CTerrain::FillIB( LPDIRECT3DDEVICE8 pd3dDevice )
{
	
	if( pd3dDevice == NULL )
		return E_FAIL;
	
	m_dwNumTris  = m_nWidth * m_nHeight;
	m_pdwIndices = new DWORD[m_dwNumTris * 6];

	DWORD count  =  0L;
	for ( int z = 0; z < m_nHeight; z ++ )
	{
		for (int x = 0; x < m_nWidth; x ++)
		{
			// create vertex index from co-ordinate

			WORD index= x + (z * m_nWidth );

			m_pdwIndices[count]=index;
			m_pdwIndices[count+1]=index+m_nWidth;
			m_pdwIndices[count+2]=index+1;

			count+=3;

			m_pdwIndices[count]=index+m_nWidth;
			m_pdwIndices[count+1]=index+m_nWidth+1;
			m_pdwIndices[count+2]=index+1;

			count+=3;

		}
	}

	// Triangle indexes

	if( FAILED( pd3dDevice->CreateIndexBuffer( m_dwNumTris*sizeof(DWORD)*3,
												  D3DUSAGE_WRITEONLY,
												  D3DFMT_INDEX16,
												  D3DPOOL_DEFAULT,
												  &m_pIB) ) )
	{
		return E_FAIL;
	}
	
	VOID *pIndices;
	if( FAILED( m_pIB->Lock( 0, m_dwNumTris*sizeof(WORD)*3, (BYTE**)&pIndices, 0 ) ) )
		return E_FAIL;
	memcpy(pIndices,m_pdwIndices,sizeof(WORD)*m_dwNumTris*3);
	m_pIB->Unlock();

	return S_OK;
}   

and for rendering:

      
pd3dDevice->SetTexture( 0, m_pTexture );
	
	pd3dDevice->SetStreamSource(0, m_pVB, sizeof(TERRAIN_VERT));
	pd3dDevice->SetVertexShader(D3DFVF_TERRAIN);
	pd3dDevice->SetIndices(m_pIB, 0 );


	pd3dDevice->DrawIndexedPrimitive( D3DPT_TRIANGLELIST, 
		                               0, m_dwNumVerts, 0, 
									   m_dwNumTris );