misunderstanding surface in civil 3d

[hamidcivil3d]

Hello

I have a qusetion about surface for so long .I show you my problem in two examples:(plz download Attachment)

1-In Surface file1 i made surface and i set contour smooth in last step but after that i see contours interfer each other!! in concept it is completely wrong but civil 3d dose it without any warning!!!!(because in this status triangles should interfer each other)(pic 1)(File 1)

2-In another file i made surface from contour and  i minimized flat area(without any smoothing) but again i see contours interfer each other(pic 2)

I'm working with civil 3d 2010

[ccoles]

You have the smoothing value set too high. Try reducing it. Made a big difference to me. See attachment.

[hamidcivil3d]

Thankyou for your reply

Yes it is right but i don't know why civil 3d creates these surfaces without any logical reason and concept .for second file it is not acceptable surface  at all.

plz download file2 from :

http://www.4shared.com/file/q13E3mNb/File2.html?

[mathewkol]

1. Smoothing:  there's nothing wrong with the surface.  The problem is the smoothed contours.  I don't use them because they are not accurate.  See the image below.  The red contours are EXACTLY where they should be given the TIN.  The grey ones (yours) are after smoothing.  They look good, but they don't represent the actual surface elevation.  Both labels read 66.25.  The red is the accurate one.  The grey is just a smoothed contour.  The elevation is NOT 66.25, but something slightly different.
2. Second file:  Again, there's nothing wrong with the surface.  Remember, "Minimized flat areas" doesn't mean "eliminate flat areas".  You may still have some, which looks like your case.  If you have a flat area at elevation 10 and you want to show a 10m contour, where should the software draw it?  That entire area in 10 so the software just decides where to draw a contour.  It's up to you to edit the sufrace to avoid this.  That minimize tool does a very good job, but it can't catch everything.

[neilyj666]

The quality of the original information will also affect the surface i.e. if the points are widely spaced then there is more scope for inaccuracies when contoured.

Additionally, the use of breaklines to define tops and bottoms of slopes (rather than only using points) can also help in some instances

[ccoles]

Matt,

To borrow from another frequent poster, Joseph D. Bouza, P.E., "All Contours Are Lies!" Smoothing doesn't make the surface any more 'inaccurate', since TINN surfaces are still an approximation. There is no telling what happens between shots in a TINN, and real world surfaces are not made of flat 3d faces pasted together with sharp edges between points. Smoothing contours is a legitimate way to make the drawings appear more real, but can easily be over-done.

I prefer to use the 'smoothing' routine in the surface edits, where I can select regions to smooth the contours instead of the entire surface. This allows me to get rid of angular contours in flat areas, but leave sharp breaks at my slope breaks. Bonus, it adds points to the surface to smooth out the contours, so the contours stay accurate to the TINN!!

[mathewkol]

The smooth surface edit; yes, very cool.

I was expecting Joe to reply here as he often does for posts about contours. I didn't want to steal his thunder 🙂

[ccoles]

Here's a visual example of what I was talking about.

This first example is an open region between my edge of pavement and a slope about 200 feet away.

I added a 'smooth surface' for a small portion of the surface using the 'Natural Neighbor' method.

And it added points to smooth out the area for me, leaving sharp edges at my slope.

I hope this is helpful!!

[hamidcivil3d]

Thank you ccoles for your sharing

Your way is new for me  and also useful