When I get the desired design, I select each part of the bridge separated and I extrude them and convert them to edit poly.

当我得到了想要的设计，我单独选出了桥梁的每一部分进行挤压操作，在编辑多边形里面进行调整。

youdao

After extruding convert the object to Editable Poly or apply Edit Poly modifier to make bottom of the wall fluently become a floor.

然后将其转化成可编辑多边形或者添加编辑多边形修改器，让墙壁的底部变成地板。

youdao

What we need to do now is to join both elements into a single object, without losing their materials. So, right-click on the teapot, Convert and Convert to edit poly.

我们要做的是将所有的元素汇集到单一的物体中，同时又不丢失原有的材质，因此我们首选要将茶壶转换成可编辑多边形。

youdao