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## How to tie two designed surfaces together?

• #### 1.  How to tie two designed surfaces together?

Posted 04-29-2020 12:19

Anyone know the best way to tie two surfaces together? I have a surface coming in at an angle and would like to make a smooth transition with correct slopes. Thanks.

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Ditch VCL.vcl.zip   1.87 MB 1 version

• #### 2.  Re: How to tie two designed surfaces together?

Posted 04-29-2020 12:50

I would find the Surface Intersection between the two without any Transitions first - TBC 5.3 has a Create Surface Intersection Line command to do that. That will tell you what you have to work with.

There is no " Magic Way" to do this - you will need to create Transition Strings (the path along which you want to transition the surfaces along. You could use Vertical Design on the new lines to transition slopes etc. You may need to use Sideslope to compute the Daylight Line Elements and then patch those together to create what you want.

It will be a combination of Create Sideslope, Create Surface Tie, Create Vertical Design and CAD that gets you to a solution, but you kind of have to draw what you want to happen - at least for the main areas (exclude Sideslopes) and then once you have worked out how the main areas come together then start applying what you want to do with the sideslopes - Vertical Design is quite helpful in this area as is the Sideslope COmmand

Alan

• #### 3.  Re: How to tie two designed surfaces together?

Posted 04-29-2020 13:50

Got it. Will try using those commands.

Thanks Alan!

Pablo

• #### 4.  Re: How to tie two designed surfaces together?

Posted 04-29-2020 16:53

Pablo

I took a quick look here and created this

Realistically you need to create the Ditch Corridor so that it extends to the end of the alignment and then Explode the Ditch Surface and turn it into Lines and then use those lines to create the Ditch Surface.

Then what I would do is make a surface of the Majenta lines for the other surface.

I would then trim back the ditch lines to where they intersect with the Main Line Ditch (assume that is what you want to happen. If you want smooth curve transitions between them then you can use Fillet to create Arcs between them to smooth out the intersection between the ditches - then elevate the arcs using Elevate Linestrings or Vertical Design to get the Elevations and ditch slopes as you needs them.

Then run the Create Surface Intersection Linestring between the two surfaces to compute where the Intersection Strings are and add the created strings to both surfaces (our RPS Macro does that automatically for you). You also want to set the Linestrings to Sharp and Texture Boundary so that you can use them as texture Boundaries for the Null texturing (Next Step)

Then I use Surface Texture, No Material (Null Texture to clip out the areas of the two surfaces that I want to remove and see where I am at at that point.

If you now want to smooth out the Intersection slopes, you can create surface Contours and then explode those into Linework and add curves to those to smooth them - or use the Spline / smooth setting on the Lines you created to round off the sharp intersections, or if you put curve radii in the Ditch Lines, you can use those to create a New Sideslope to Daylight as you see fit - this will be the time consuming part for sure - getting it to look good.

• #### 5.  Re: How to tie two designed surfaces together?

Posted 05-03-2020 03:15

I took a slightly different approach; not having the surface intersect macro. After extending the corridor as Alan did, I created an isopatch surface from the two adjoining design surfaces, then generated a contour at elev. 0, explode it and spliced it into both surface's boundaries, creating 2 surfaces that were bounded at their intersection. Then just merged them to combine into one surface.

The first method I tried was to extend the corridor the same way, but only to the point at which the flowlines met, then simply merging them using the "Keep minimum"  type of merge. But when using that type of merge, the program clips the resulting merged surface to use only the area that the source surfaces overlapped, even though no clipping was set. Perhaps @Alan Sharp can explain why the resulting merged surface is clipped (bounded by overlap) rather than a complete combine even without a clipping boundary set. (2nd pic)

Yet other ways would be:

create a 3d linestring at the intersection by exploding the 0 elev. contour and drape it onto either surface. Then break and clip unneeded linework and use the rest to create the final surface.

OR

Merge using "Keep minimum" as shown in second pic, create a surface edge breakline and use it as the boundary to clip linework inside.....

• #### 6.  Re: How to tie two designed surfaces together?

Posted 05-16-2020 05:52

Sorry Steve - I missed the need to respond here - apologies

I cannot say that what we do is Right or Wrong here and am open to input as to what people expect that I would feed back into development, and I could of course question what we do here - however I think the logic here is as follows

If you have two surfaces in my picture below shown as two rectangles. The Larger Rectangle is at Elevation 100 and the smaller rectangle at say 95. There is as you can see an Overlap Zone. The current Merge options are

1) Merge - Maximum - this will create a small surface where the two surfaces overlap only and would be at elevation 100

2) Merge Minimum - this will create a small surface where the two surfaces overlap and would be at Elevation 95

3) Merge - Finish Replaces Existing - in this Case Finish is Surface 2 and Existing is Surface 1 (great terminology in the dialog ....) and you will get a composite surface where the overlap is cut out of the Existing and the Design is dropped in, and then based on Breakline Approximation Parameters as to how much densification you have going on on your linework in the original surfaces you will get varying degrees of steepness of slope and results - note that the Merged Surfaces are always based purely on what the source surfaces look like at the time of the merger and that can generate quite different results as you can see below - the above case is poorly densified data, the lower case is more densified data

We can debate what should happen when you say "Keep Minimum" or "Keep Maximum" - by definition, the two surfaces have to exist at the interpretation point in order to determine which is the Min or Max, in areas where there is only one or other of the two surfaces we could choose to Keep that surface or not I guess, and the developers evidently decided that they should only keep the data where the two surfaces overlap. You could of course argue the other way around and keep a surface everywhere one exists and keep the minimum where the two overlap. I think the thought process here was that if you have an Existing Ground all over the site and you have a Design cut out of it, that when you merge the two using keep Minimum you would get the surface that you have to excavate and if you use the Keep Maximum you would get the surface you have to Fill and if you use the Finish Replaces Existing then you would get the end result surface where the Design is cut into the existing to give an idea of how the site will look once completed.

Of course as soon as you develop a tool for one purpose, people then find uses for it for other purposes and so the tools design intent is now morphed into something somewhat different to the original intent and it can be seen to "n longer work right"

I would be interested to get peoples input on this and how a tool like Merge can be used in different scenarios that may require the tool to be modified in order to better suit the purposes you want to put it to

For me - if two surfaces don't tie correctly before merger, then Merging them is asking for trouble as you will likely never get the right result and I guess that is why I don't use this tool for much other than cutting a Design into Existing - but if we can make it more useful for other tasks please capture them here, provide example data of what you are starting with and what you are trying to achieve and we can for sure look at it.

Based on your question I am assuming that you are suggesting that Keep Min should take the lower of the two surfaces where they overlap, and take whatever surface is there when they do not overlap - so keep Min would look like this

Note the Flags where the two rectangles meet because the two surfaces do not tie together nicely / properly at that location - and without using the source linework to form this surface - you are going to have to explode the TIN to get at the Triangle Edges to fix these issues (merge does not have the linework of the source TINs in the resultant surface)

and if you used Keep Maximum it would look like this

Again - note the Flags and incorrect triangulation because again the two surfaces do not tie together correctly at the outset - so Merging will not fix that and because there are so many variants of data, and people create so many "scenarios" it is extremely hard to predict what is the "right thing to do" in every scenario - however if you have examples of where the tool would work better when you have done the right things to the data - like Offsetting the lines to make the Ties work, or adding sideslopes to tie the surfaces correctly before merging where an overlap scenario is in play - please share and we can discuss.

What you are looking for above is more likely this

and the Merge tool will not solve this as there is a lot of interpretation that is required to make this happen and additional breaklines that have to be created etc.

I hope that this answers the initial question Steve, but I am sure this triggers a lot of discussion which I would love to hear here if possible

We all want the "Big Red Easy Button" for sure ....

Alan

• #### 7.  Re: How to tie two designed surfaces together?

Posted 05-14-2020 07:25

@Alan Sharp Did you ever have a chance to look at my previous post? I'm still curious why "Keep minimum" clips the resulting surface only to use overlapping areas without any boundaries selected...

• #### 8.  Re: How to tie two designed surfaces together?

Posted 05-14-2020 08:19

In my experience, it helps to think about how an operator on a dozer would tie the two surfaces together.  It seems to me to be more about getting creative than a certain command to use.  I would certainly extend the top and toe of slope to see how they intersect, but so often, it is a lot of hand drawing that just ends up looking right and making sense.