제가 정육면체의 그림을 다이렉트를 이용해서 그리려고 하는데 밑에는 초기값과 라인을 그리는 코드 인데요

실행하면 라인이 몇개는 그려지고 몇개는 안그려지는데 왜 그런건지 좀 알려주세요

m_vFieldPos=D3DXVECTOR3(-13,0,-13);

 m_vFieldLineX=D3DXVECTOR3(1,0,0);
m_vFieldLineY=D3DXVECTOR3(0,1,0);
m_vFieldLineZ=D3DXVECTOR3(0,0,1);

void Area::FieldLine( void )
{
D3DFVF_XYZ_COLOR line[13];

  line[0].vPos = m_vFieldPos;
  line[0].color = 0xffff0000;

  line[1].vPos = line[0].vPos + m_vFieldLineX * 26;
  line[1].color = 0xffff0000;

  line[2].vPos = line[0].vPos + m_vFieldLineZ * 26;
  line[2].color = 0xffff0000;

  line[3].vPos = line[2].vPos + m_vFieldLineX * 26;
  line[3].color = 0xffff0000;

  line[4].vPos = line[1].vPos + m_vFieldLineZ * 26;
  line[4].color = 0xffff0000;

  line[5].vPos = line[0].vPos + m_vFieldLineY * 52;
  line[5].color = 0xffff0000;

  line[6].vPos = line[1].vPos + m_vFieldLineY * 52;
  line[6].color = 0xffff0000;

  line[7].vPos = line[2].vPos + m_vFieldLineY * 52;
  line[7].color = 0xffff0000;

  line[8].vPos = line[3].vPos + m_vFieldLineY * 52;
  line[8].color = 0xffff0000;

  line[9].vPos = line[5].vPos + m_vFieldLineX * 26;
  line[9].color = 0xffff0000;

  line[10].vPos = line[5].vPos + m_vFieldLineZ * 26;
  line[10].color = 0xffff0000;

  line[11].vPos = line[7].vPos + m_vFieldLineX * 26;
  line[11].color = 0xffff0000;

  line[12].vPos = line[6].vPos + m_vFieldLineZ * 26;
  line[12].color = 0xffff0000;

D3DXMATRIX mTM;
D3DXMatrixIdentity(&mTM);
g_pDevice->SetTransform(D3DTS_WORLD, &mTM);
g_pDevice->SetFVF(FVF_XYZ_COLOR);
g_pDevice->DrawPrimitiveUP(D3DPT_LINELIST, 12,
  &line[0], sizeof(D3DFVF_XYZ_COLOR));
}