Converting a 2D into 3D

[Ra'ad]

I have very slow performance when converting a 2d feature line into a 3d feature line .

THE PROBLEM
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The problem is that when I create a 3D poly line from a 2D feature line it takes a long time to do. It takes 10 minutes per 1000 meter feature line on a surface made of 5m x 5m point levels. The problem when you need to convert al long poly line such as 7 Kilometre long into 3D, it takes more than 1 hour time to convert it.
THE QUESTION IS
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1- Why is this very slow performance and how to reduce the performance time and make it faster ?
2- What are the recommended steps, PC specifications to reduce the performance time ?
3- Are there another factors that my cause such slow performance ? wat are they ? and how to resolve them?

THE STEPS OF THE SPECIFIC FUNCTION
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- A new drawing ( Autodesk civil 3D Metric NCS Base .dwt) is opened.
- A copy is made from another drawing of natural ground levels (NGL) and pasted in to the new drawing. The size of the NGL drawing is 6171 KB.
- Surface is made on the basis of Drawing objects ( NGL: natural ground levels).
- 2D drawings is made on the surface (NGL) with poly lines.
- Feature lines is created from the 2D poly lines.
- From edit feature line – Elevation from surface – a 3D poly line is created. Now It takes 10 minutes to convert a 1000 meter Feature line in to a 3D feature line on a grid of 5m x 5m made surface.
- The total size of the drawing is 15000 KB.

PC SPECIFICATIONS
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PENTIUM 4, 3.6 GHz single core, 2 GB RAM, 250 GB HD, PCI-e graphics card from NVIDIA Quadro FX 3450/4000 SDI.