grading from feature lines

[Lath]

I am obviously a beginner on civil 3d..

I have a created a surface from contour lines.

I have drawn a feature line and assigned elevations (it slopes down from 3.5m elevation to 2m elevation). I have added grading from the feature line to the existing surface but have not merged the feature line with the surface.

I also have to make a low area (elevation at 1.5m) on the surface and know i need to grade at 1:1 from the feature line to the low point. Is there a way to grade from a feature line at a given grade (1:1) to a known height (my low point at 1.5m) without drawing another feature line for my low point? Seeing as the height of the feature line varies I can't just offset it at the grade.. I.e. the grade is the constant here.

I will have a few walls and lower / higher areas to grade to. I have drawn the top of my wall and mounds and have assigned them elevations but not sure whether to now make them all feature lines and try to merge with the surface by grading at a set grade or to do some sort of infill.

Sorry - any responses will have to be fairly basic for me to understand.

Thanks very much 🙂

[Neilw_05]

To grade to a specific elevation you can create a Grade to Elevation criteria. There should already be a criteria for that in the default C3D templates that comes with the product.

As for how to grade your site I suggest you run through the grading and surface modeling tutorials that come with the product first. That will give you a better understanding of how to build surfaces from gradings and feature lines. The tutorials can be accessed through the help system.

[Joe-Bouza]

I may be interperting you incorrectly, but when you say "but have not merged the feature line with the surface" it sound like you may be thinking about having your grading effect the EG surface you made from contours. If that is correct I'd would suggest you create a new surface FG that you can compare. If you have to blend together you can do this with pasting operation and perserve the integrity of EG. I know you said basic reply but I'm sure you can handle it

[Lath]

Ok thank you both very much for your replies. I have now made a new Grade to Elevation criteria.

I had a go at creating a new surface FG and adding the FL but seemed to get stuck somewhere along the way (I'm trying to create a series of basins).

I have a few FL at different elevations. Should I..

1) add the all  the FL tto the new FG surface as breaklines,

2) then grade them all to the elevations that I know (with my new grade to elevation criteria),

3) and then merge with the existing surface EG.

Or is that completely the wrong order to go about this?

Thanks again

[Neilw_05]

A typical workflow is to create a proposed grading surface and add all your gradings into that. Then you would create a composite surface representing the proposed surface merged into the existing. To do that you would create a new empty surface and paste in the EG surface, then the proposed. This is better than pasting into the EG surface directly because you want that surface to remain intact incase you need to update it with more survey data, etc. Any edits to it will be propogated to the composite surface since it is linked by the paste operation.

[Lath]

Great thanks. I was on something else for a while but now I am giving it another shot. 

Pasting the two surfaces seems to work quite well 🙂

I have added a boundary to my FG surface because it is curved and higher the EG - so combining the two looks a bit whacky. I have been grading at 1:4 from the feature lines on the FG to the EG..

Is it possible to grade between the EG and FG in a way that cad will just work out the 'neatest' grades to do this along the whole featureline? Instead of using 1:4, the grades would be different along my entire FL as it is over an existing slope. (Proposed curved mound that slopes into an uneven existing surface). I just want a gentle looking slope and at the moment I'm getting my mound then a channel and then the existing surface.

I also have to draw a 3d rectangle underground and would like the contours on my new surface to reflect this. I have drawn a 3d rectangle in the correct space but can't seem to make it work like a FL - i.e.  'add to surface as breakline'. What is the alternative command for grading around 3d solids? I am loathe to put two FLs on top of one another (1 for the topb of the box and one for the top) as this never seems to work.

Sorry - more silly questions. Thanks again for your help!

[troma]

I don't follow the question about grading between surfaces. I think posting a picture might help.

As for the breakline—go to the prospector, find your surface, expand the definition, right click on breaklines and click 'add'. You can use 3D polylines or 2D polylines as breaklines.
You can also have two featurelines on top of each other at different elevations, no problem as long as they are in different sites.