User's Guide

Virtualwind SketchUp Plugin Tools   →   Correcting Geometry   →   Common Problems

Common Problems

You are committed to making a fully watertight model, you know what tools are available, you are armed with an arsenal of strategies – you are well on your way to correcting models. Still, you find yourself looking at an Edge and wondering, "Why is the Check tool insisting this is wrong? It looks completely fine!"

To help with those situations, the following section lists the usual suspects when you come across this scenario. This is by no means meant to be an exhaustive list: every time you try to convert a model, you may find something new and unexpected. Even if you do not find your exact problem among the chief suspects below, hopefully some of them will point you in a promising direction.

Missing floors: Missing floors are the most obvious problem you will come across: look at the model from the bottom, and if you can see in, its floor is missing. The only way around it is to fix the floor. SketchUp's auto-fill feature is very useful for that: you can often close an entire floor, no matter how complex, with a single line thanks for the autocomplete feature.

Interior faces: Most geometry has interior faces: faces on the inside of the model. For example, you might have a two-story house with the second floor modelled. More often, there are several layers of interior geometry: as you delete the inner-most face, you will find a second interior face. Regardless of why it is there, you will have to get rid of it: interior faces are not allowed in watertight geometry.

Auto-filled interior faces: The Auto-fill feature can be overeager, filling in faces that you did not intend – and often did not expect. Sometimes these unexpected faces will be impossible to visually detect (although the Check tools will never fail to pick them up). There is no way around this: you just have to accept that you will have to occasionally delete extra faces.

Overlapping geometry: It is possible in some situations to create faces and edges that are exactly coincident: they occupy the same space, but they remain two (or more) separate objects. Usually, the best way to deal with them is simply to delete them all, and re-fill any gaps in the geometry that appear as a result. These are often difficult to detect. Sometimes, overlapping faces will appear to "shimmer" when you rotate the model. (A face-shimmer almost always indicates overlapping faces, but not all overlapping faces shimmer.) Overlapping edges are impossible to visually detect, but usually they will disappear if you use the Remove Zero-Faced Edges tool. If that does not work, keep selecting and deleting edges until they are all gone, then fill in the resulting holes by using the Line tool.

Razor-thin gaps: "Razor-thin gaps" are miniscule – sometimes undetectable – gaps in geometry. They most often occur when you have exploded an overGrouped component. Sometimes, you can connect the geometry by dragging one edge until it "snaps" to the other edge, but this does not always work. If it does not, it usually means that the lines are not parallel. You can try instead to drag one of the vertices, but that does not always work either. In the worst case, the easiest thing to do is just delete the face, then recreate it.

These can be notoriously difficult to detect, because the gap is sometimes so miniscule that no amount of zoom-in will reveal it. If you suspect that a gap is present, select the edge that is giving you the problem and delete it. If there is no gap, all the faces connected to that edge should get deleted as well. If one face (or several faces) don not get deleted, that means the deleted edge was not actually connected to it, which it turn means there was a gap. Do not bother recreating the edge you just deleted; instead, fill the hole you just created by using the Line tool and relying on the Auto-fill feature.

These gaps can sometimes actually be "overlaps": the geometry overlaps by a miniscule amount. The detection and solution tricks for overlaps are exactly the same as for gaps.