SAC- Intersection Points of 2 Surface Links

[Umit.Arslan]

Hi everyone

            I am trying to build a general stripping soil pkt in SAC and i started with creating 2 surface links (EG and Graded Surface). Next, i want to find out the intersection points (6 points) as shown in the picture (may be more than 6) to determine the cut/fill points.How can i find out the intersection points (P1-P2-P3-P4-P5-P6) of the 2 surface links?

Thanks

[KMercier_C3D]

In Civil 3D I would create a TIN Volume Surface comparing these two surfaces. I would then extract the contour(s) at elevation 0 of this volume surface (since this shows where the intersection points are). 

In SAC I would create a subassembly that would reference both surfaces but also have multiple Target Offsets (one for each of the maximum number of transitions you expect). Your flowchart would need to check if each subsequent Target Offset ISVALID and then determine if between the points is in a cut or fill to do your necessary shapes. 

[Umit.Arslan]

i couldnt understand how to deal with the multiple target offsets.Is that mean i have to number all targets and seperate them like target1, target2. in the drawing?And also i have to clasify all targets as fill and cut?

[KMercier_C3D · Accepted solution]

Yes all the targets in Civil 3D would need to be selected and you would treate them in SAC as Target1, Target2, Target3, etc. You do not need to determine cut/fill in C3D. You would just need to determine in SAC with the first set of surface links which one is at a higher elevation than the other, then at every target they would switch. You could do the comparison using L1.MaxY>L2.MaxY to confirm if L1 is above L2. 

The benefit to setting up a subassembly like this is that it doesn't matter what the original subassembly that made the proposed surface was, it will still work (so if you have a combination of slopes and ditches or anything). 

Alternatively you could build this into a subassembly which just has one Surface Target Parameter. And the Input Parameters defining the slopes/widths/etc of the proposed surface. And you can then use a Surface Link to define the existing surface and then find the intersections using the Slope To Surface, or Delta X to Surface. 

[fcernst]

Kati,

The IsValid API was confirmed defective in SAC.

We have to test dummy points to see if they move as a workaround. Do you know if this has been addressed in 2015?

Here's the link:

http://forums.autodesk.com/t5/AutoCAD-Civil-3D-General/SAC-Using-OffsetTarget-IsValid-as-Decision/td...

Thanks

Fred

[Umit.Arslan]

i created the attached pkt file but somehow it is not working properly and couldnt find where i made the mistake and in some cases my sample line is intersecting the target1 polyline several times then i have to break up the polyline into piecies and taget them  as 2,3,...Also i am wondering if there is a much more simple way to create this kind of pkt file?

Thanks