Topic: (C3D 2008) Creating a proposed surface

[Guest]

What's the "recommended" way of creating a proposed surface?  In LDT we would draw polylines then convert to aec contour objects, draw a boundary around the new contours (boundary would "touch" the ends of the contours), then we would create the terrain through the terrain manager.  Would this same practice carry over to C3D?  Is there a better way?  How are others doing this?

[sinc]

It's basically a completely different process these days.

Now, you would use more-intelligent objects such as corridors, grading objects, and/or feature lines to create the design.  Contours would NEVER be drawn directly, but fall out of the model automatically.  If a single composite FG surface is desired for the end product, it would be created by combining the EG surface with the various design elements, by pasting them together.

[sinc]

Contours would NEVER be drawn directly, but fall out of the model automatically.

Oh, and I suppose I should mention the exception to this.  There's a phenomenon I call "contour jitter" which can crop up as a side-effect of generating contours from a TIN.  Basically, instead of seeing nice, smooth curves, sometimes the contour gets "jagged".  Most of the time, this can simply be ignored, since most people understand why it happens.  But if the jitter gets really bad, like it does sometimes, or if the CAD tech is really anal, sometimes people like to draw nice, smooth contour lines over the "jitter", and use the hand-drawn contours instead.  But this should really be the ONLY time you ever hand-draw a contour in C3D.

[Guest]

It's basically a completely different process these days.

Now, you would use more-intelligent objects such as corridors, grading objects, and/or feature lines to create the design.  Contours would NEVER be drawn directly, but fall out of the model automatically.  If a single composite FG surface is desired for the end product, it would be created by combining the EG surface with the various design elements, by pasting them together.

Ugghh...  I'm not sure that particular approach would jive with the way we do things here.  Basically we have designers that sketch up something, then the cadd monkey/jr. designer will input it into LDT.

The image below shows how we do things now (LDT).  The outer yellow pline is the boundary, the inner one is the building footprint and the red is obviously the contours.  So now with C3D we HAVE to use the grading objects, features lines, etc... to create what you see below?

[mjfarrell]

The BEST way would be to have survey data for the ground shots and breaklines, and then add the point data and break lines to the model. The model will then add its own boundary for you.  Matt keep in mind that when you build a surface from contour data, that the contour data is itself only accurate to 1/2 the contour interval, and is adversely affected by any 'weeding' settings you applied when adding it to the surface.. In otherwords it may or may not be accurate.  So go get the survey data, and start building accurate models from this point forward.

Also note that C3D does NOT use aec contour objects, they must be exploded down to polylines for the surface model to use them.
Even though the command is Add Contours, it wont use contour objects.  :ugly:

[mjfarrell]

Yes you need to change the way you design and draft entirely.  Civil 3d is a design tool that drafts, so if you want to make money, the engineer or designer needs to use C3D, or the draftsperson needs to be trained to design.  Or your competition will do it this way, and you folks will soon be out of work (profits).

[dfarris75]

You can, meaning you have the ability to, draw "contours" and assign them to a surface as breaklines, however, in a way that defeats the purpose of building a model and would be considered "backwards modeling" so to speak. A 3D model is built so you can extract information and data from it. Build a model correctly as proposed by Sinc and Mike and then it will generate the contours for you.
The only time I use contours is when it's all I have to use or like Sinc said, when you get the jagged contouring. Then I might add a fake contour as a breakline to smooth it out. Otherwise, it's best to use the grading features, corridors, points, etc. to build your model(s).

[Swift]

Just keep in mind those 'jagged contours' are a sign of bad triangles underneath.

[sinc]

Just keep in mind those 'jagged contours' are a sign of bad triangles underneath.

Well, not really.  This phenomenon I call "contour jitter" is not a sign of a bad surface, or bad modeling.  It's simply an artifact of the fact that an irregular surface is being approximated by a bunch of flat triangles, and contour lines are generated by drawing straight line segments across the face of each triangle.  Sometimes, the nature of the terrain means that the contour should really be something more like a spline, but because contours are generated the way they are, we end up with "contour jitter".

Basically, there are no "good triangles" that can eliminate the jitter.  If you vastly increase the number of triangles, you can reach the point where the line looks smooth, but if you zoom way in you'll still see the jitter.

[dfarris75]

In a recent case of "the jitters" it was merely due to the fact that I had pasted two surfaces into a new surface and the jitters occurred in-between where there was no true surface data. I added "contour breaklines" as data to fill in that gap and voila, the jitters were all straightened out. Thus you can see that "the jitters" are caused by a lack of data in said area(s), generally speaking.

At any rate, I say go with Mike's advice and use the program as a design tool which is what it's meant for. This is the best way to approach the situation from all angles of the work.

In my mind the engineer should use the program to do preliminary design; to get his bearings on and find what direction he wants to take with the project. Then it should be handed off to the draftsman who should be trained to do design and would have the ability to carry out details and revisions. Later of course after the draftsman has honed his design skills the engineer could give the project to them from the beginning and play more of a q.c. role alleviating him/her of valuable time that he can spend conducting meetings with clients, taking care of red tape related to projects, shaking hands and kissing babies (acquiring more work and/or making friends with local politicians/bureaucrats), drinking beer at the local pub, etc. The next step would be to train the designer/draftsman to handle other aspects of project management. This is good for the draftsman as it provides him/her with new avenues to pursue in his career and keeps him/her from getting bored. It also establishes a strong business model where each person within a company is trained to assume the role of their supervisor/manager, not to mention it's a wonderful way to attain a higher level of employee moral which will strengthen the company as a whole.

Thank you. Please, no applause.

[dgreble]

The golf course is also a good place to drum up business.

I do agree that in the wake of Civil 3D all persons in the office should know both the program AND design otherwise you and your company will be left behind.  I know of another firm that has laid someone off because of Civil 3D and the fact that the person did not know how to "design".

We sometimes get the jitters as well but those can easily be smoothed out.