When cleaning up a surface, I've always created an Outer Boundary to define the surface limits so that the triangles wouldn't go where I didn't want them.
I'm trying prepping in hopes of sitting for my Autodesk Civil 3d Certification exam at AU. The chapter I'm currently reading through talks about deleting triangles from the surface.
So now I'm wondering about the pros and cons of both methods.
Any advice would be greatly appreciated.
This is my opinion and MAY or MAY NOT agree with the official ACAD answer.
I see the boundary approach as the method to use to clean the edge of the tin surface to avoid the weird contours that are not correct at the edge of the surface due to erroneous "reaching for solution" along the edges. Also Boundary is good to trim a Huge surface down to the area of interest.
I see delete line as a "fine tuning" thing for when a few lines are showing up that should not be.
Now the boundary thing is a one shot clean up and can be toggled for "applied or not" at build time.
Delete lines are deleted. They show up in a huge list in your edits, but it is much harder to go between show them/don't show them status. You actually have to delete the edit and good luck figuring out which is which.
Also with delete lines, I have noticed that if you delete all lines going to a point but do not delete the point, you may get strange things going on with the point reinserting itself with future edits. So then there is the delete point aspect of deleting lines. If there is a boundary and the point is outside of the boundary then you do not have these surprises.
Boundaries tend to be cleaner and faster for MASS editing.
Delete lines tend to be cleaner and faster for smaller tweaks (don't forget the points)
You can automatically clean up those areas by setting the Use Maximum Triangle Length to Yes and then specifying a distance. This will keep you from having to delete all those lines, as they will automatically delete the line(s) longer than the distance specified. However, you must be careful and check your surface to make sure it didn't put any "holes" in the surface. If that is the case, then make your distance longer. This option is in Surface Properties, Definition tab, expand Build.
TRogers: that sounds like another viable option. But like you said, gotta be careful not to create any holes.
I was originally looking for pros and cons for the two specific ways of cleaning up the edge of a surface. I hadn't even thought about other methods of cleaning it up.
So if there are any other options, I'm open to expanding the list. But I really would like to get a good feel for the pros and cons of the various optoins.
I tend to avoid the maximum triangle length because of unpredictability. there are many areas in surveys that are uniformly graded/sloped that cause topo points to spread out relative to areas that require more detail. Because of this, I rarely if ever use the triangle length option. Now, having said that, if you have a topo that has regularly or reasonably regularly spaced shots, the triangle length option is a good one. I just don't see topos matching that definition often.
I don't know if it makes a difference in perfomance (I'd think that processing the numerous deleted triangle edits would have a greater impact than processing a boundary) but I think it comes down to which method is most efficient. In Land Desktop I usually found it most efficient to delete the unwanted triangles and then generate a boundary for the edited TIN, add it to the surface and dump the edits. It was just easier for me to drag a fence line across the TIN lines vs. picking vertices with a polyline to trace the boundary.
There is another tool that you could look at for the edge triangles: "Maximum angle between adjacent TIN Lines" What this is looking for are the very long flat triangles that happen around the edges of a TIN. By default this is turned off and the default angle is 90. Try turning it on and I typically start at around 120-150.
Could you tell us if there is any significant difference in impact on performance for the different workflows?
Max Length / Max Angle should be about the same with a fixed outer boundary (data clip boundary) being a little faster. That said, what I would do is use the max Length / Angle to get my surface and then extract the boundary, turn off the max Length/Angle and add the extracted boundary back into the surface.
I would only add the boundary into the surface after I was sure there would be no additional edits to the EG.
While we're talking about boundaries, look at the new option to add a surface as a boundary to another surface. It is a great way to cut FG into a copy of EG.
Peter is onto something here.
use the triangle length and angle functions to trim the perimeter down to what it should be.
Then extract the boundary. use that linework to create a boundary of the original untouched surface.
This removes the issue of varying lengths of internal triangles or any other "HOLES" created while cleaning up the edge.
If for some reason you get a line removed by mistake along the edge using the automated approach, you can tweak the extracted boundary edge before applying it.
NOW I think we are onto something.
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