Impossible Crease Line

You get this error when the geometry on both sides of the crease line belongs to the same polygon. The problem is that the crease line is about to fold something that is supposed to stay flat.

Basic example

Let’s start with a basic example:

This is an O-shaped polygon with a single crease line. The crease line needs to fold one element against another, but this is actually the same element and it must stay flat.

A more realistic case

It is pretty difficult to make this mistake on purpose. It usually happens when some other crease line is ignored because of being incorrect. Here’s a more realistic example:

The crease line on the right is hanging and is ignored because of that. This makes both top and bottom parts of the dieline the same and triggers the “impossible crease line” error for the crease line on the left.

What to do?

This problem is usually found in complex dielines with misaligned elements. The best fixing strategy is to locate the other problem crease lines and fix them instead. They are usually reported before this error, so fixing errors top to bottom works best.

If the shape has folding animation, it sometimes helps to fold and unfold the shape to identify the crease lines that don’t work and check them for errors.

Want More Hints?

• Almost Vertical/Horizontal — crease line is probably misaligned;
• Broken Shape — shape is broken apart when folding;
• Path Is Not Closed — the dieline needs a solid, continuous outline path;
• Crease Line In Main Outline — the main outline must be made of cuts;
• Intersecting Curved Cuts — it might not be easy;
• Empty Layout — why there is no dieline visible?
• Hanging Element — what if a path goes nowhere?
• Impossible Crease Line — a crease that shouldn't be;
• Inconsistent Crease Lines — similar crease lines must have same angles;
• Invalid Crease — crease lines have limitations;
• Overlapping Lines — cut and crease lines must not overlap, as well;
• Separate Element — the dieline should come in one piece;
• The Points Are Too Close — avoid crowded spaces;
• Z-Fighting — what to do with overlapping polygons.

There's more from the older folding engines:

• Intersecting Holes — holes must not overlap;
• Impossible Shape — some shapes simply don’t exist;
• Outside Hole — all holes must be inside the outline path;
• Misaligned Elements — ends must meet, perfectly;
• Elements Are Too Small — keep dieline paths simple;
• Triangulation Failed — Origami fails to make a 3D mesh of a dieline.

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