Slope Grading Weirdness

[sshuler]

I just started using the grading capabilities and have had really good luck.  I'm grading a berm down at 3:1 slope to catch the existing grade.  It has worked fine for several iterations until I moved the berm slightly.  Now when I grade the feature line out at 3:1 it appears to work correctly for most of the length except a few areas where itleaves gaps and doesn't appear to meet the existing contours.  I can't figure out why this happens or how to fix it.  Any help is appreciated.  Screen capture attached.

[sboon]

There are two common problems that you might be running into.  Either your grading object runs off the edge of the surface in some locations, or you accidentally changed some of the elevation points along the controlling feature so that the slope doesn't catch.  Try doing a quick profile through the grading object and slide it around to see what is happening in a section view.

[sshuler]

Thanks but the feature line is extremely simple and the elevations all check.  The grading doesn't go off the edge of the surface it's supposed to catch.  The only thing I can think of is that I want it to grade DOWN to catch grade but in those areas it thinks it needs to grade up because the existing surface is actually higher for a very short distance.  Somehow I think I have to make it cut the existing surface for a short distance then grade down to catch it again.  That's probably quite confusing but it makes sense to me.  I just haven't worked with the grading enough to know how to trick it in those areas, if indeed that is the issue.

[kidkuts]

In that case in those areas you need to grade down to a specific elevation, otherwise there is nothing to target.

[Joe-Bouza]

That is odd, because if you select grade to surface criteria you would be prompted for slope in cut and slope in fill. In which case the slope chosen is not enough to catch existing at the given distance

[troma]

Try adjusting the criteria.  There is a setting to search for a cut solution first, then fill, or vice versa.

Update:

Grading downhill is a fill

Grading uphill is a cut.

It makes sense in the end, but can be confusing at first.

[sshuler]

Thanks for all the replies.  I did try setting the cut slope criteria to be the priority.  That didn't work.  I finally gave up (for now) and moved my feature line over slightly to eliminate the computer thinking it needed to fill up in those isolated spots.  That did the trick.  Tells me I'm on the right path.  I need to work more with combining grading elements verus trying to accomplish it all with one feature line, I think.  ALways something to learn...

[troma]

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@sshuler wrote:

Thanks for all the replies.  I did try setting the cut slope criteria to be the priority.  That didn't work.  I finally gave up (for now) and moved my feature line over slightly to eliminate the computer thinking it needed to fill up in those isolated spots.  That did the trick.  Tells me I'm on the right path.  I need to work more with combining grading elements verus trying to accomplish it all with one feature line, I think.  ALways something to learn...

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I thought you said you wanted it to go downhill?  Just to reiterate:

DOWN is FILL

UP is CUT

[Joe-Bouza]

I'm puzzled - I thought the OP wanted to catch existing ground. Doesn't the criteria for grade to surface account for cut and fill condition?

[sshuler]

To clarify (hopefully), I have a berm whose finished grade in almost all areas be higher than existing ground.  Grading to a surface at a slope works fine in all those areas where FG is higher.  The computer correctly FILLS to grade in these areas.  However, there are some very isolated areas where the existing grade is very slightly higher than design grade (less than a foot).  In those areas the computer appears to CUT to existing grade at the designated slope and stop.  What is odd, though, is that there is not a smooth or clean transition between the CUT and the FILL.  The daylight line makes abrupt direction changes and the contours that result do not intersect existing contours as you would expect.  Please look at the image attache dto the original post to see what I mean.

[Joe-Bouza]

Might I suggest you elliminate the small cut by first grading at a distance like 3 feet at 2% and then daylight

[troma]

Of course Joe, you're right.  But in certain circumstances it would be possible to find both a cut and a fill solution, depending on the existing topography.  That is why there is a setting for the "Search Order" to tell C3D what to look for first.  If you tell it to look for fill first, and there is no solution with fill, then it will find the cut solution.

Some of what was said earlier suggested the OP's problem may have been related to this, but now I don't think it is.

[Joe-Bouza]

Search order? Thats new to me t. Where is that setting?

But it seems the OP geometric issue is tiny cut adjacent to big fill...Oh Are You saying this search order can force a fill in a cut condition?

[troma]

Here:

No, it will not force a fill in a cut condition.  It just tells it which solution to look for first.

I don't think this is related to the current situation.  (Earlier I had thought it might be.)