Rectangles break into hidden triangles

Occasionally I will draw a rectangular plane and later when I try to modify it I notice that it has fractured into random triangles with hidden geometries. Why does this happen, how can I prevent it from happening, and how can I fix it if it happens again?

Most often when that happens it’s because at least one corner has been moved very slightly out of plane. Sketchup, being a surface modeler, tries to maintain the faces even if that means adding additional edges.

Avoiding it is done by ensuring that things stay in plane. One thing that can help with that is turning off Snapping in Model Info>Units. Otherwise making sure you stay on axis when moving things is the main thing.

Your surfaces are being fractured by moving other connected parts of your model around which change the location of the bounding edges of that surface, making it not a plane… Learn to model using groups and components to isolate geometry so it does no interact with other parts.

I’ve seen this sometimes in a complex object that I’ve (sometimes carelessly) modified many times with cuts.I think @DaveR and @endlessfix describe the reasons well. I think once you get it, it’s not often fixable --anyone?

The faces seem to be just slightly off and cannot decide where to be. You can sometimes delete the edges and the plane will work as one, only to have hidden edges return later.

Much obliged, gents. I turned off the snap and we’ll see what happens.

One unfortunate part of seeing these, often even turning off snapping doesn’t save your model. Once the small errors are there they tend to continue, error begets error.
Some people have struggled for days when they could have started from scratch and redrawn in no time.

In the early stages, I’m a throw it out and start over guy . But we get some fairly complex models going and it’s a real buzz kill when it happens.

But I just thought I’d try the community approach for a change. I appreciate the responses.

Make sure you set your templates with snapping off so you don’t walk into it again.

Ha, right. Thanks again.

If there is only one, or a few, hidden lines on the face, you can often fix it by moving a corner (one with only two unhidden edges) roughly normal to the face (use an arrow key to lock the move axis) and snapping the move to the face on the other side of the hidden line. That gets both parts back in plane, and you can then delete the hidden line without losing the face.

Repeat if necessary snapping to the face beyond the next hidden line.

Nice! Thanks.