How to Use Interference Checking in BricsCAD BIM

Quick answer: Interference Checking is a modeling-phase tool that finds conflicts by comparing 3D solid models of building elements, interference occurs whenever two 3D entities overlap in space. -INTERFERE finds intersections between selected entities, or across every element in the model at once, and optionally creates interference solids on their own layer, set by INTERFERELAYER.

This is now the fourth page in this hub whose own title reads “BricsCAD Lite & Pro” despite being filed under BricsCAD BIM, alongside DmPushPull, Making Parallel Copies of 3D Solids, and the Rhino/Grasshopper integration page, a consistent pattern of general tools documented within the BIM section.

Performing an Interference Check

1. Select the 3D solids to check and launch -INTERFERE (multiple solids select via a selection box or the Structure panel; the Command line reports how many entities are in the set, for example “Entities in set: 20”; the Nested Selection option lets you select 3D solids inside blocks and Xrefs too).
2. Select more solids to add to a second set for comparison. Pressing Enter without selecting anything for the second set compares the first set’s entities against each other instead.
3. Press Enter to run the check.
4. An interference volume creates for each collision, shown as a solid displayed in red (since it sits on the Interferences layer). Adjust these settings by typing S for Settings while the command is active, or clicking Settings in the prompt menu; the Interference Settings dialog lets you toggle Create interference solids, and shows the current Layer and Color used for them.
5. To fix an unwanted intersection, turn off the Interferences layer, then use a 3D solid modifying tool like BIM Drag (covered on this hub’s Using Drag page) or Subtract on the interfering solid to correct the model.
6. Run -INTERFERE again to confirm everything’s fixed; if there are no collisions left, the Command line reports “Solids do not interfere.”

Frequently Asked Questions

What happens if I press Enter without selecting a second set of entities? The first set of entities gets compared against each other instead of against a separate second set.

How do I know an interference check came back clean? The Command line reports “Solids do not interfere” if there are no remaining collisions.

Can I check for interference between entities nested inside blocks or Xrefs? Yes, use the Nested Selection option to select 3D solids inside blocks and external references.

Where do the created interference solids get placed? Their own dedicated layer, set by INTERFERELAYER, displayed in red by default.