Managing the swapping of Triangles

This question comes up a fair bit - you use the TBC Swap Triangles function and as soon as you make a change to the surface the surface reverts all the swapped triangles back to how they were. This was the case until a recent version of TBC - I am guessing 5.50 but maybe earlier, however in 5.51 for sure this has been fixed so that swapped triangles are maintained after a surface rebuild provided that the area covered by the triangles that were swapped is not affected (you did not add or remove points or lines in that area from the surface).

However - if you are running an older version of TBC that does not support the locking of the swapped triangles, the following applies.

  1. Check that you have the surface property called Adjust Flat Triangles set to Yes
  2. Check that the Flat Triangle Tolerance is set to a value that works - this normally works at 1’ but you may need to change it to say 2’ - it certainly works
  3. Use breaklines instead of swapping triangles - use the new Takeoff Lines command and set the Override Segment Length to checked on - this will stop the new line getting subdivided by the Surface Breakline Approximation parameters in Project Settings - Computations. Draw the breaklines on their own layer and set the layer properties to Not Printable - that way you can see them and turn them On and Off but they will not come out on a drawing. Also in Takeoff Lines command you can add the lines you create to the surface so that when you start a New line they are added automatically and your surface updates to reflect the changes - eliminates another step.

Hope that this helps