Create building plans
Introduction
Thanks to new laser scanners, either static or mobile, drawing 2D/3D plans of an existing building, thanks to a point cloud, is probably a very common task you have to deal with. You may use to draw manually on ortho-images or on cloud slices. This practical exercise shows how 2D plans can be drawn in an assisted way.
Exercise overview
In this exercise, we see how to create 2D plans and elevations. The AEC license is required for these computations.
Several steps are included in this exercise:
Define the slices,
Extract, draw and edit the polylines,
Export this drawing to another CAD software.
The file used in this tutorial is ScanToPlans.3dr
Overview
This file contains the point cloud of a 3-level building that was measured with a Leica BLK2GO. Thus, panoramic images have been recorded while measuring. The cloud has been resampled to achieve a mean distance of 1 cm between points, nevertheless the following workflow can be performed with higher density.
An UCS has been defined parallelly to the building, activate it, then select the cloud and launch the workflow Scan to Plan.
Slice definition
In this first step, you will define where to draw building sections.
Set the slice direction to Z=1. Select the option List of distances and click the blue cross. You can either enter a value or click an elevation in the 3D scene. In perspective mode, you can go inside this building to understand its architecture and pick appropriate elevations. In orthographic view, press X or Y key to pick levels thanks to an elevation view. Here is a list of useful sections to combine:
|
Level |
Distance (m) |
Thickness (m) |
Comment |
Suggested name |
|
0 |
1 |
0.2 |
main section |
0-Main section (Z) |
|
0 |
3.1 |
0.2 |
below ceiling |
0-Below ceiling (Z) |
|
1 |
3.8 |
0.2 |
floor |
1-Floor (Z) |
|
1 |
5.2 |
0.2 |
main section |
1-Main section (Z) |
|
1 |
6.6 |
0.2 |
below ceiling |
1-Below ceiling (Z) |
|
2 |
7.3 |
0.2 |
floor |
2-Floor (Z) |
|
2 |
8.7 |
0.2 |
main section |
2-Main section (Z) |
|
2 |
10 |
0.2 |
below ceiling |
2-Below ceiling (Z) |
|
2 |
10.25 |
0.1 |
ceiling |
2-Ceiling_a (Z) |
|
2 |
10.4 |
0.1 |
ceiling |
2-Ceiling_b (Z) |
When the list is fulfilled, set the default slice thickness (20 cm) and click on Insert slices. They are added to a list of slices where you can rename (which is highly recommended, the names will be exported as well) and modify them. You can adjust their positions and their thicknesses through the 3D scene. For instance, reduce the thickness of 2-Ceiling_a (Z) and 2-Ceiling_b (Z).
Now, you can add vertical slices:
|
Direction |
Distance (m) |
Thickness (m) |
Comment |
Suggested name |
|
X |
11 |
0.2 |
central area |
Central area (X) |
|
X |
18.4 |
0.2 |
stairs |
Stairs (X) |
|
Y |
2 |
0.2 |
stairs |
Stairs_a (Y) |
|
Y |
6 |
0.2 |
stairs |
Stairs_b (Y) |
Finally, set the resampling step to 1 mm and click Compute. This will project the points on defined planes and then resample the clouds to eliminate duplicate points. That is why the initial point cloud density can be higher or lower than this sample. Click NEXT button to validate and start plans extraction.
Fig1: extracted slices
Extract plans: level 0
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Select the slice 0-Below ceiling (Z) and extract automatically (with a 0.04 m resolution) the external contour. Choose seed points in straight lines. The resolution parameter should be set approximately to the half of the wall thickness to detect each side. 4 cm should fit most cases. Note: if the mean distance between points is too high or if you have missing areas in your point cloud, the extraction will stop automatically. In such cases, switch to Manual extraction to continue. |
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The automatic extraction finds the corresponding wall and the neighboring ones. The points used by an extraction are automatically hidden (and cannot be used again for automatic extraction). To check the extraction, click the funnel button to display them. |
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At any time, you can modify manually the extracted polylines (refer to Edit Polyline), for instance when the extraction ends in a noisy area. Here, press SUPPR to remove selected vertices. Note it is possible to select several vertices thanks to a rectangular selection, regardless if they are displayed with a red ball or not. |
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3 polylines can be extracted. Their default colors are yellow (after extraction) and green (after edition). Now, you can copy this level to 0-Main section (Z). This level has been automatically activated and you can complete 0-level with other details such as doors, windows... |
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Automatic extraction of details requires clouds with high resolution and accuracy. Here, you can try the manual mode. While manual editing, you can click the funnel icon to display the points used by previous extraction. Draw manually this polyline, then add a new vertex (snap it to another one). |
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Extend a segment: press SHIFT and click the purple polyline to extend the segment to the nearest intersection of the lines. |
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Draw manually the doors, then add 2 perpendicular segments (press SHIFT and click the red polyline). Maintain CTRL key to draw parallelly to the screen when it is possible. |
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Insert vertices to complete the plans. |
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Level 0 is complete:
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Extract plans: level 1
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Once 0-Main section (Z) is done, copy it to level 1-Main section (Z). Yellow polylines match the level 0. Switch directly to slices 1-Floor (Z) and 1-Below ceiling (Z) and repeat the process explained for 0-level (extracting and cleaning lines on 1-Floor (Z), then copying those lines to 1-Main section (Z). Then do the same for 1-Below ceiling (Z) to 1-Main section (Z). Blue polylines correspond to 1-Floor (Z) and red ones to 1-Below ceiling (Z). You should notice some differences: walls may have another thickness (4 and 7) or the plan may be different (1, 2, 3, 5 and 6). |
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Then, remove unnecessary polylines and complete the extraction of 1-main section (Z). Here, only the magenta polyline has been added. Others have only been removed or edited. For instance, you can select all vertices, while editing a polyline, and move them to translate it. Note that each level can be slightly or totally different, thus it is often not necessary to start a new level copying the previous one. It depends also on the accuracy and level of details that you want. |
Extract plans: level 2 and vertical sections
Optionally, complete plans extraction with 2-Main section(Z), 2-Ceiling_a (Z), 2-Ceiling_b (Z), and the 4 vertical slices.
|
Level 2 |
Details on the ceiling (Level 2) |
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Central area (X) |
Stairs (X) |
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Stairs_a (Y) |
Stairs_b (Y) |
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Click NEXT button to validate and start next step.
Export 2D Plans
At this step, you can generate a DXF file, send the polylines to AutoCAD or generate a FML file. Choose to export a DXF. Then you will be able to add texts, hatches... and complete your plans and elevations.
Fig 2: DXF (main levels, ceiling and vertical sections)