RECAP RCS or RCP to C3D

[apweng]

Hello,

I am not fully understanding the difference between RECAP export RCP and RCS files?  Specifically, does it matter which format I use to export to Civil 3D?

Thanks,

Andrew

[Pointdump]

Hi Andrew,
Here's my understanding:
The RCP(P=Project) file is a pointer to a "Support" folder that contains, among other things, an RCS file.
The RCS file is an everything-all-in-one file.
Neither one is "better" than the other, and both are perfectly usable in C3D.
Dave

[apweng]

That's fantastic thanks Dave!

Andrew

[apweng]

Hi again Dave thanks for the response - very helpful!

We're trying to figure out best workflow for decimation - basically RECAP or C3D simplify surface.  The latter seems to be the best option as it appears to provide better control for decimation (for example removing 90% of points such that maximum elevation difference is 0.1').

We're not sure how decimation works in RECAP.  For RCS export are the following options...

1. Decimate ground points to 90% (leaves 10% in ground and moves 90% to model key) - and export ground points to RCS
2. Decimate ground points to 10% (leaves 90% in ground and moves 10% to model key) - and export model key points to RCS

When importing RCS to C3D using these options, the number of surface points is not the same, but very close.

Other questions relate to...

1. Decimation option when importing point clouds to RECAP (up to 10mm)
2. Decimation when exporting RCS
3. C3D Create Surface from Point Cloud - distance between points - yet another option to "simplify" a surface 

Many questions here and just trying to optimize the workflow for the best result.

Andrew

[Pointdump]

Andrew,
Decimation in ReCap seems insufficient to me, but I haven't tried it lately, so maybe they've improved it.
Simplify Surface is what most folks use. Works very well. BUT...if the dreaded MMS has already been created, then you might have a hosed drawing. My favorite method is number 3, "Distance Between Points". As you're creating a surface from the ReCap file, keep "Total number of points selected" to under 2 million.
Dave

[neilyj666]

I'd agree with @Pointdump that you need to avoid MMS files at all costs.

I'd also add that in Civil 3D 2026, it is possible to data shortcut a partial surface which may improve performance and reduce drawing size -I'm not using 2026 day to day yet so haven't got any more information regarding this feature but looks like it could be very useful.

[ChicagoLooper]

@apweng 

Decimation in RECAP is controlled in Advanced Scan Settings.  The Advanced Settings are established before importing your file. Not after.

1. First setup your file and folder. 

2. Next, click the Advanced icon. Use the slider to set your decimation, then click IMPORT (the import button not shown, it's in lower right).

 

[Pointdump]

Andrew,
Playing with different workflows to decimate points in a point cloud containing 3,057,627 Pts:

1. Using ReCap's upfront Decimation Grid maxed out to 100mm only decimates to 2,173,726 pts. You still need to filter Ground(2) pts before exporting the RCP file.
2. In C3D, using "Distance Between" option set to 5ft produces a surface with 32,743 pts. Fiddly, but do-able, and gives you a good granular-level decimation.
3. Using ReCap's Intelligent Decimation set to 10,000 points produces a C3D surface with 9988 pts. Nice thing is you can pull those points out of only Ground(2) classification points.

Dave

[neilyj666]

The max decimation of 100mm is too small in my opinion for ground models probably as Recap seems to be promoting itself for building scans etc where I can understand 100mm being the maximum

[Pointdump]

Neil,
"The max decimation of 100mm is too small in my opinion for ground models..."
I agree. Entirely inadequate.
Dave

[apweng]

Thanks for all the responses.

Recap PRO has 2024 has  decimation tool...

This works reasonably well but we are doing our decimation on the C3D surface as we have more control there over which points are removed.  We're using just the Ground classification points for export to RCP/RCS for C3D consumption.

Andrew