Tailoring Triangulation

Very useful tool - indispensible in fact.

To respond to your immediate problem, I would point out that what you get is not a 'void' in the triangulation, but that you get 'null triangles' (if I recall correctly trimming a triangulation using the linemode options works the same way).  This means that when you come to create contours, it won't contour those triangles. So the effective 'void' is in the contour model.

It's important to ensure that the PBRK string is as close as practicable to the model feature you actually want to to be the limit. The point interval should be no greater than that of the relevant feature string.  So take for example a roundabout island where you don't want to contour within the kerb line: create a parallel string, offset say 15mm inside the circle of the kerb line. 

Further notes that might be helpful:

• It's the points of the PBRK string that matter, not the string itself. So the one PBRK string can jump around doing its magic at various places.
• You can create a 'library' or 'resource' model in which you store various strings that could be useful as PBRK strings. If they are stored with your conventional labelling for temporary strings (for me that's x y or z, or mx my mz etc), then you can copy into your model (which is to be triangulated), rename as PBRK, run the triangulation, then delete the PBRK string. You can even assemble a new PBRK string from various ones stored in your library model, using EDIT 008 or 012. If you use input files generally for design, you can generate the strings in the library automatically, and thus they will adapt to any changes in the design.
• In simpler cases it may be more efficient to not bother with PBRK, but create a boundary string (previous bullet point applies for those too!) and use that to trim the contour model: but that get's complicated and time-consuming (even in input files) if you've got more than one or two 'voids' to create.

Hope this is helpful - have fun. Let me know how you get on.

Very useful tool - indispensible in fact.

To respond to your immediate problem, I would point out that what you get is not a 'void' in the triangulation, but that you get 'null triangles' (if I recall correctly trimming a triangulation using the linemode options works the same way).  This means that when you come to create contours, it won't contour those triangles. So the effective 'void' is in the contour model.

It's important to ensure that the PBRK string is as close as practicable to the model feature you actually want to to be the limit. The point interval should be no greater than that of the relevant feature string.  So take for example a roundabout island where you don't want to contour within the kerb line: create a parallel string, offset say 15mm inside the circle of the kerb line. 

Further notes that might be helpful:

• It's the points of the PBRK string that matter, not the string itself. So the one PBRK string can jump around doing its magic at various places.
• You can create a 'library' or 'resource' model in which you store various strings that could be useful as PBRK strings. If they are stored with your conventional labelling for temporary strings (for me that's x y or z, or mx my mz etc), then you can copy into your model (which is to be triangulated), rename as PBRK, run the triangulation, then delete the PBRK string. You can even assemble a new PBRK string from various ones stored in your library model, using EDIT 008 or 012. If you use input files generally for design, you can generate the strings in the library automatically, and thus they will adapt to any changes in the design.
• In simpler cases it may be more efficient to not bother with PBRK, but create a boundary string (previous bullet point applies for those too!) and use that to trim the contour model: but that get's complicated and time-consuming (even in input files) if you've got more than one or two 'voids' to create.

Hope this is helpful - have fun. Let me know how you get on.