Jiggly corrupt-looking model - What is it, and how can it be fixed?

The Symptoms

The symptoms of this issue are 'jiggly' or corrupt-looking geometry, especially curved or cylinder-type geometry such as pipes, handrails or anything that is not a flat plane. The geometry also 'wiggles' as you zoom, pan, or rotate the camera or view, as shown below.

The level of 'Jiggly Wiggly' can vary; a more extreme example is as shown below.

Another symptom of this issue is that zooming in and out may feel a bit 'wiggly' and not as smooth as expected, along with the inability to select objects accurately. For example, clicking on an object might select a different object and, in extreme cases, even disallows selection altogether.

What is the Issue, and what causes it

This technical term for the issue is a 'Floating point Issue', and this type of issue/problem exists in almost all 3D software.

In a computer's 3D environment space, there is no such thing as 'infinity', and the 3D space must have a boundary extent in the 3D words, else the computer would be unable to calculate the environment and run out of memory, trying to calculate infinity. Because of this, behind the scenes, almost all software has a limit to the size of the 3D world space.

This is calculated from the software's internal' 0,0,0 coordinate to the geometry in the space, and the further away from the 'Internal 0,0,0 point', the less accurate it will be, as the computer sacrifices accuracy for scale.

Most of the time, this is not an issue, as unless your building is more than 800 miles from the software's internal 0,0,0 point, this would not be noticeable at a fraction of a mm 0.000000m.

How to Prevent it

In most 3D software, the internal 0,0,0 point sits in the centre of the screen when you create a new project. Thus, in theory, if you start modelling, your project will be close to the internal 0,0,0 point and thus not cause any issues. Remember that the 'internal coordinate' is different from the shared/global coordinate system or local coordinate system and lives unknown in the background.

It is also good BIM practice that the lead consultant shares a master coordinate file with the rest of the team who are producing 3D models. This ensures that the internal coordinates are the same in all models produced (which helps, as below).

Okay, but I have an issue, and I can't start the project again! How can I fix it?

If the design team has followed good practice, changing the coordinate system from Global to 'local' will fix the issue. This essentially tells Twinview to move the internal coordinate point to the local 0,0,0 point. If you only have one model or if all models have the same internal coordinate point (as described above), then when you re-open the project, the issue will be resolved.

It's fixed the 'Jiggly Wiggly'; however, my multiple models are no longer aligned.

This is because the models, when authored, did not utilise a master coordinate file to ensure all models have the same internal coordinate 0,0,0 point. To resolve this, the models would need to be translated and moved back together to align them again.

On the model tab, clicking on a model to open its dialogue allows you to enter an X, Y and Z offset value to move the model. All values are in mm and, when set, will automatically apply this transform whenever the model is shown/opened.

To get the data to enter into the offset fields, you can use the dimension tool to get the X,Y, and Z offsets between two models, as shown below.