V17 Face division defect

bug

#1

I have copied the following section of walkway from my castle model…

I created a new empty model and pasted the face at the origin, and also used Paste In Place. These 2 faces were then grouped, and a different material applied to the group…

The face nearest the origin divides into 2 correctly (resulting in a total of 3 faces)…

However, the other face ‘divides’ into 6, with the parent group material applied!!!..

I have attached the simple test model so that you can reproduce this scenario for yourselves.

You will not fully comprehend the frustration and the amount of time this defect is wasting!

If there is any explanation, workaround, or fix coming soon, I would very much like to know.
V17 face division defect.skp (22.9 KB)


#2

Sorry to say, I can’t reproduce what you describe on my Mac, though maybe I don’t understand what if any additional steps I am supposed to apply to make it happen.

When I open your model I see a large group with a red material applied to it. Inside it I see two faces, one at the origin and one at the diagonally opposite corner of the group. Both of these faces are painted with a gray material. That gray material dominates the red one applied to the group (which is what is supposed to happen). Neither of the faces is split into subfaces - I’m not clear what action is supposed to cause that to happen.


#3

Neither of the faces are split, yet - because that is what you do to each, as shown, to reproduce the bug!


#4

Your edge’s are not coplanar. As a result, additional faces are formed.


#5

Interesting! - but if the original face is happy with its edges, how can any 2 constituent faces not be? Moreover, this face (and many more similar in my model) are defined by SketchUp using its own tolerances, which are evidently being inconsistently applied, particularly when at a distance from the origin, despite having 64-bit accuracy available. (The identical face nearest the origin divides correctly). Lastly, what is the excuse for creating SIX faces as a result of dividing one?! and not re-applying the original material?


#6

OK, after your clarification I can reproduce the error. What is happening is that SketchUp is creating extra coincident faces when you draw the edge across. These extra new faces don’t have a material assigned, so they get the containing group’s material. You can confirm all this by selecting one of the red faces and deleting it (may need to delete more than one - I had one case where there were two extras!). When you get rid of the extras, the originally assigned material is again visible.

I can confirm this is happening by probing the model contents, but at this point I can’t explain why. The edges of the original shape are split into more segments than seems necessary, but so far as I can see they are coplanar (and must be, else SketchUp wouldn’t have accepted the original edges to define a face).

This strikes me as a bug.