Precautions when using Modify - Move Vertex(Edge)

Q. The model is distorted when I use Modify - Move Vertex(Edge).

A. There are rules in CIM that are followed to retain shape. Distorted shapes may result if these rules are overlooked.

1. Changing Section Shape using Edit Vertex(Edge)

Move Vertex(Edge) provides a model editing feature that is similar to the STRETCH feature in 2D CAD.

Move Vertex(Edge) is a shape editing feature with a high degree of freedom, but this feature occasionally exhibits shapes that are different from what is expected from the user.

This is because unlike 2D models, 3D models need to adhere to rules to retain their shapes.

Let’s look at the Move Edge example below. (The example of this feature is separated as shown below due to the differences in the target properties, but Vertex and Edge are basically the same in terms of operation.)

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Figure. 1 Move Edge Example-1　

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Figure. 2 Move Edge Example-2

The two figures above are previews of two Box examples where one edge of the box is moved in the -Z direction (left example) and in the -Y direction.

The change applied to the shape Figure. 1 accurately corresponds to the user’s intent, but the change applied in Figure 2 results in a distorted shape that is difficult to predict.

The cause of this shape distortion in the 3D model is due to the tendency of the X/Y/Z axis behavior to maintain the shape of the plane that forms the object.

Once the user know the shape retention rules of the 3D model, it will be easier to understand.

The prerequisites for the Solid geometry in Move Edge are as follows:

Based on the two premises stated above, we will now go over the Move Edge process using the model in Figure. 3 below.

1. When the Target Edge is moved using Edit Edge, the vertex that forms the edge moves as well. As the edge moves in the -Y direction, the vertex also moves in the -Y direction, causing the shape of the face attached to the vertex to change.

2. The path of the corresponding vertex is
   Face①② : Within the Infinite Face*
   Face③: Outside the Infinite Face. (shape cannot be maintained with 1 plane)
   _{*Infinite Face - Plane area that extends the existing face infinitely}

3. If the four points that form a rectangle do not exist on a single plane, Face③ must perform one of the following three actions.
   　

In the process above, CIM creates a shape using step C to maintain the condition of the plane of the first surface.

Therefore, to allow the Move Vertex (Edge) feature to function correctly, consideration should be given to whether the condition ‘the face that is attached to each point that will be moved maintains a planar shape’ is followed.

2. Comparing the shape changes by the Edit Vertex (Edge) feature

• Change in section geometry by the Move Vertex feature

• Change in section geometry by the Move Edge feature