The work area (user interface) > Viewports > Viewing > Visualizing interference
  
Visualizing interference
You can easily visualize regions of interference using the Visual Interference setting. It displays intersections of all parts in the viewport. Regions that clash or interfere are shown in red.
To turn visual interference on,
1. Right-click in the viewport and select Viewport Properties. The Vport: vport1 dialog box opens.
2. Click the Visual Interference check-box in the Viewport dialog. Interference is highlighted in red in the viewport
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Visual Interference is not the same as finding interference volumes in parts using the Clash command. Visual Interference is a graphical approximation, but Clash is an accurate measure of part interference.
Limitations
Visual Cap must be turned on in the Viewport dialog.
Visual Interference is available on systems supporting OpenGL only.