struct BoundBox
{
	BoundBox();

	bool isPointInside(D3DXVECTOR3& p); //是否包含点

	D3DXVECTOR3 _min;
	D3DXVECTOR3 _max;
};
BoundBox::BoundBox()
{
	_min.x = -Infinity;
	_min.y = -Infinity;
	_min.z = -Infinity;

	_max.x = Infinity;
	_max.y = Infinity;
	_max.z = Infinity;
}
bool BoundBox::isPointInside(D3DXVECTOR3& p)
{
	if (p.x >= _min.x && p.y >= _min.y && p.z >= _min.z &&
		p.x <= _max.x && p.y <= _max.y && p.z <= _max.z)
	{
		return true;
	}
	else
	{
		return false;
	}
}

ID3DXMesh* BoxMesh = 0;
const float Infinity = FLT_MAX;
BoundBox boundingBox;

加载模型

bool ComputeBoundingBox(ID3DXMesh* mesh, BoundBox* box)
{
	HRESULT hr = 0;

	BYTE* v = 0;
	mesh->LockVertexBuffer(0, (void**)&v);
	//计算边界盒（第一个顶点的向量，顶点数，，每个顶点大小，最小点，最大点）
	hr = D3DXComputeBoundingBox(
		(D3DXVECTOR3*)v,
		mesh->GetNumVertices(),
		D3DXGetFVFVertexSize(mesh->GetFVF()),
		&box->_min,
		&box->_max);

	mesh->UnlockVertexBuffer();

	if (FAILED(hr))
		return false;

	return true;
}
ComputeBoundingBox(Mesh, &boundingBox);

D3DXCreateBox(
		g_pd3dDevice,
		boundingBox._max.x - boundingBox._min.x,
		boundingBox._max.y - boundingBox._min.y,
		boundingBox._max.z - boundingBox._min.z,
		&BoxMesh,
		0);

绘制模型

D3DMATERIAL9 white = white_mtrl;
white.Diffuse.a = 0.50f;

g_pd3dDevice->SetMaterial(&white);
//模拟碰撞或点击
if (boundingBox.isPointInside(D3DXVECTOR3(1, 1, 1)))
{
	g_pd3dDevice->SetRenderState(D3DRS_FILLMODE, D3DFILL_WIREFRAME);
	BoxMesh->DrawSubset(0);
	g_pd3dDevice->SetRenderState(D3DRS_FILLMODE, D3DFILL_SOLID);
}