How to use Clash detection?

What is Clash detection?

Clash detection is an engineering tool that automatically calculates potential collisions between different structures in the model. Calculation is done with plain geometry information that makes it possible to calculate collisions between any model elements. 

Calculating collisions

Clash detection is started from the Analyze tab. 

You can choose to calculate collisions between multiple model groups. In a typical situation clashes are calculated between different design disciplines like constructions and water/sewage pipes. When the main group is selected, subgroups are also included in the calculation.

Ignore hidden groups – an option to only calculate between visible groups.

Include self-intersecting – an option to ignore clashes between the same groups.

Merge distance – if the distance between collisions is less than the merge distance, collisions show as one clash.

For example if the merge distance is 5 m, by default, the merge distance is 1 m.

You are able to set group properties, such as Value and Tolerance, under Group Properties.

Tolerance is additional distance around objects that is taken into account in clash detection. With Tolerance users can calculate clashes with a “safety margin”, meaning that clashes that are not hard collisions but close enough will also be displayed as results of clash calculation. For example, a clearance distance of 0,1 (NOTE: the decimal place is a comma not a period) would show clashes for pipelines that are 0,1 units away from each other even if they do not collide. 

Value is meant for prioritizing clash results. Value can be any number describing the importance of a group. Value is used to sort and filter clash results so that the most important clashes can be resolved first.

If a group has subgroups, clash value and tolerance propagate to subgroups when the main group has value and tolerance set and a subgroup has empty values.

The Calculate button will start clash calculation. As result of calculation, all clashes are shown in marked red in the model and a new Clash Results panel opens with a list of all the clashes found in the model. 

Clash results panel

For each clash the Clash results panel shows: 

  • Resolution for each clash a resolution type can be selected:
    • Waiting
    • Valid
    • invalid
    • Resolved
  • Id = clash ID
  • The groups between which the clash was detected 
    • Group A, Group B
  • Clash type
    • hard clash = the geometry goes inside the other geometry
    • clearance = the geometry is within clearance distance from other geometry
  • Size = clash size
  • Value = the sum of values between clashing element groups
  • Tolerance % = when objects are not clashing physically (hard clash) but they are clashing within tolerances, clash results will show it as a soft clash with distance and tolerance % how much tolerances overlap
  • Risk value = Value * Tolerance%
  • Status
    • New – not detected before
    • Old – detected previously but not detected anymore
    • Recalculated – the same, detected again
  • Resolution as stated before
  • Comment = a free field for comments

Results can be sorted by any column mentioned above.

Column filtering

Columns can be filtered different ways

  • Group A, B, Clash Type and Comment using wildcards * (star) or ? (question mark).
  • Size, Value, Tolerance by > (greater than), < (smaller than) or = (equal to). 
  • Colums that use numeric value allows to set new filter under filter risk.

The filtered column will show * (star) marking and by right-click of the mouse will access the filtered information.

Clash result taskbar

Create or delete topics from a clash taskbar.

  • In Clash results tab select wanted result row, select Create topic and thumbnail is automatically created to Topic list tab.
    • By fefault he topic description will be record groups names, value, size and comments.
  • Move to Topic list tab and open the information by double clicking the thumbnail.
  • Topic Editor will open on the righthand side of the window and Edit wanted iformation and save changes. 

The Show only selected groups option will turn all other groups off when showing clash calculation results and show only groups specific to the clash. This will make it easier to see where the clashes are and find, for example, clashes that are underground. 

When Show only selected groups is on, Create Topic saves the group state that is currently on that is specific to the clashes.