Layer / tag

A layer or tag sorts the objects in a drawing or model into classes that can be switched on, off and managed together. Walls sit on one layer, furniture on another, dimensions and text somewhere else. The same file can then produce views suited to quite different purposes.

How programs differ

In 2D drafting programs such as AutoCAD a layer carries more than visibility: it also holds line color, linetype and lineweight. Whether a drawing set reads properly on paper depends largely on how its layers are organized. SketchUp calls this function a tag and uses it mainly for visibility. SketchUp has a well-known rule here: raw faces and edges stay untagged, and tags go on groups and components. Ignore it and hiding a surface can leave its edges behind, breaking the model in confusing ways.

Using them in visualization

Tags make a render scene much easier to handle. Keeping trees, people and cars on their own tags lets you hide them while modeling, so navigation stays quick. Put design options on separate tags and two alternatives can be rendered from the same camera with almost no effort. Saved scenes remember which tags are visible, so each view comes back with a single click. In architectural offices, a shared naming standard for layers prevents confusion as files move between teams.