Jiggly corrupt looking model - What is it and how to fix it.

in this support guide we will discuss how to fix an issue known as 'Jiggly wiggly' which causes model geometry to appear corrupted and object selection to behave un-expectantly.

What we will need

• Your original 3D models as uplaoded to Twinview

• A basic undertanding of World/Global coordante systems

⏰ Time: About 30 mins Difficulty Level: 🍺 📺 Video Tutorial Available

The Symptoms

The symptoms of this issue are 'jiggly' or corrupt looking geometry, especially of curved or cylinder type geometry such as pipes, handrails or anything which 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 a object might select a diffrent object, and in extreme cases even dis-allows selection all together.

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 computers 3D environment space, there is no such thing as 'infinity' and the 3D space must have an boundary extents in teh 3D worls, 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 softwares 'internal' 0,0,0 coordinate to to the geometry in the space, and the further away from the 'Internal 0,0,0 point the less accuracy 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 softwares internal 0,0,0 point this would not be noticeable at a fraction of a mm 0.000000m.

The same issue exists in Revit and other 3D software and its why Autodesk recommend that you dont start modelling more than 500miles from the projects internal coordinate 0,0,0 of that your project is more than 500 miles long.

The softwares 'Internal coordinate' is not the same as the more familiar Shared coordinate, or local coordinate. The software coordinate is normally a hidden coordinate system that is hard coded, and the other coordinate systems are mapped to. In some software you cannot move or change the softwares 'internal' coordinate 0,0,0 point.

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, so in theory if you start modelling your project is going to be close to the internal 0,0,0 point and thus not cause any issues. Remember that the 'internal coordinate' is different to the shared/global coordinate' system or local coordinate' system and just lives unknown in the background It is also good BIM practice that the lead consultant share a master coordinate file with the rest of the team who are producing 3D models, this ensures that the internal coordinate'is the same in all model produced (which helps as below).

Okay but i have the issue, and i cant start the project again! How can i fix it?

If the design team have followed good practice then 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 them when you re-open the project the issue will be resolved.

Its fixed the 'Jiggly Wiggly' however now 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. The way to resolve this would be to translate and move the models back together to align them again.

On teh model tab, clicking on a model to open its dialogue allows you to enter a 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.

The Edit model modal showing the model offsets overides

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

Using the dimension tool to get vales to move/translate the model

Remember that the offset values are in mm, and the dimension tool shows in meters by default. Change the unit type in the dimension settings to mm and the precision to make your life easier.