point cloud autocad

7/21/2019 Point Cloud AutoCAD

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POINT CLOUD PROCESSING IN AUTOCAD

Raffaella Brumana, Luigi BarazzettiPolitecnico di Milano

GICARUS Lab.via Ponzio 31, Milan & via Previati 1/c, Lecco (Italy)

http://www.icet-rilevamento.lecco.polimi.it/

[email protected]

[email protected]

This short manual describes the use of point clouds in AutoCad 2015. A small project

made up of 4 registered scans is illustrated:

- Scan 061 and scan 063 = ground floor;

- Scan 137 = courtyard;

- Scan 161 = first floor.

The object is Castel Masegra, Sondrio (Italy). Please use the following link to

download the example dataset (612 MB):

https://www.dropbox.com/sh/vda0qocmh94h0az/0MCfrHrEeT

As things stand at the present (2014) point clouds can be managed in AutoCAD for

Windows. AutoCAD for MAC does not support point clouds. This means that students

with a MAC need Windows installed on their machine (Bootcamp can automatically

install Windows). It is important to remember that AutoCAD 2015 does not work onWindows Xp.
mailto:[email protected]:[email protected]:[email protected]://www.dropbox.com/sh/vda0qocmh94h0az/0MCfrHrEeThttps://www.dropbox.com/sh/vda0qocmh94h0az/0MCfrHrEeThttps://www.dropbox.com/sh/vda0qocmh94h0az/0MCfrHrEeTmailto:[email protected]:[email protected]


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Data description:

The dataset example.zip can be downloaded from the Internet. Files must be

unzipped before they can be used.

The folder contains:

- autocad_example.rcp = this is the project file. It allows one to open the whole

dataset (you need a good machine in the case of large projects composed of

several scans);

- another folder autocad_example Support with independent scan files (061.rcs,

063.rcs, 131.rcs, 163.rcs). This files can be used when you need only some

specific scans (this is good when memory issues arise).

An important consideration deserves to be mentioned: a real laser project can be huge

(billion points) and the whole dataset is several gigabytes. This could be the case of

the dataset of our course. In this case you must follow theprocedure able to load only

a limited number of clouds (see next section). Alternatively, as students have a specific

part of the building, useless scans can be removed (*.rcs file from the Windows

folder). Another solution is the scan manager tool (see next sections).


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Data processing in AutoCAD:

First of all, the scale of inserted objects can be set to meters: command units

You can import (i) the whole dataset or (ii) only a limited number of scans. This choice

depends on your machine and the size of the dataset. The dataset used in this short

manual is small and both solutions are feasible. In the case of large projects the use

of few point clouds is a good choice.

In both cases, data can be imported into AutoCAD with the UCS set to WORLD(point

clouds are registered in this global reference system).

You can use the command Insert Attach to import the whole dataset. Select the

file autocad_example.rcp in the main folder and disable translation, scale, androtation options (see next figure). The laser project has a fixed reference system that

cannot be modified. In other words, the point cloud should be preserved (commands

like scale, move , etc., are prohibited). The point cloud is registered in a fixed

reference system (geodetic network with total station in this case). The different parts

(scans) of the project can be automatically merged when the reference system does

not vary.


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Click on the point cloud to activate the POINT CLOUD MENU

Select Scan Colors and then Intensityto color the points(tip: Hardware acceleration

should be on)


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The POINT CLOUD TOOLBAR has a Point Cloud Manager Toolthat allows us to handle

different clouds. This is useful when only a limited number of scans is needed.

If you need only a limited number of scans you can import (Insert Attach) only thefiles inside the folder autocad_example Support.These .rcs files correspond to the

different scans of the project. The procedure is the same previously described, but

you can import only 1 file (one by one).


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If you want to extract a horizontal slice (e.g. for the plan of a building) you can change

the point of view (from top to front). You can draw a horizontal line where the new

plan is needed (e.g., 1m or 1.2 m above the average floor level). Therefore you need

a horizontal line. Then you can create a parallel line with the command offset.

Click on the point cloud and select Rectangular. You can now crop the point cloud and

obtain a thin slice made of points. You need a thin slice (e.g. 1 cm, 2cm) because walls

are not perfectly vertical!


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You can change the point of view (from front to top) in order to visualize the

perimeter. The reconstruction can be carried out with the command plinewithout

snap.

Remark: lines must be drawn with the command pline. The objet snaps (F3) must

be off (exception made for the closure). An example is shown in the following figure


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The same procedure can be used for vertical sections and facades, but you must set

a new UCS.

The reconstruction of the faade (see next figure) can be carried out by drawing apline that gives the direction of the faade. This pline is the reference object for

the new UCS.

Command ucsyou can set the direction of the X axis as follows:

(1) (2)


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You can choose the direction of the Y axis in order to obtain the new UCS.

(3) (4)

The project has a new UCS that can be renamed as followscommand ucsman

Right click on the unnamed UCS: the new name can be Facade, then Set current

Select the option Orthographic UCSs, relative to Facade, Front, Set Current


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If you want to remove the previous clipping box used for the plan you can select

Uncrop Allfrom the POINT CLOUD TOOLBAR

You can create a new polygonal clip that contains only the facade


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Finally, you can change the point of view (from Top to Front). You can draw with the

command pline.

Final remarks

AutoCAD 2015 is still a little bugged. For instance, the visualization of points inside a

thin slice (e.g. 1 cm) could be carried out by drawing two parallel lines. Then, the

rectangular selection tool can be used to select only the points belonging to the slide.

This is what you can see without zooming: the cloud and your two lines, which

become a single line in this visualization (obviously, this is a 1 cm slice).

A zoom on the left and right sides is needed when you want to crop the cloud with

the rectangular tool. On the other hand, the cropping tool of the clouds has a

fundamental drawback: you cannot use the zoom because there is a variation of the

area (you should try it for yourself).


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As things stand at the moment you can draw two small lines on the opposite sides to

identify the exact location of the area.

Then, you can select the area with the endpoint snap (without zooming).

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