JRC 3D Reconstructor - Gexcel · Select a scan and save a 2D image from your scan 2. Edit in black color the area to delete using any external software (i.e. Photo Point, Coral Draw,

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JRC 3D Reconstructor

PRE-PROCESSING

JRC 3D Reconstructor Pre-processing

In this tutorial you will learn how to

Filter/Pre-process data

- automatic noise removal

- automatic computation

1. Overview 5. Contacts4. Results2. Noise Removal 3. Computation

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Load a Grid point cloud

The toolbar reminds the user the suggested workflow steps

Pre-processing is the first workflow step after scan import. All the grid point clouds have to be pre-processed before going on with data elaboration even though the data have been already filtered in a third party software.


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IMPORTANT NOTE: preprocessing step works only with Grid Cloud of Points A Grid cloud of point can be viewed as “image” where the

number of pixels (pix) are equal to the number of point the scanner has acquired (valid and invalid).

In the preprocessing parameter you will find MASK BORDER (pix). This parameter

define the dimension in pixels of a square mask (“the kernel of the filter “), which give

you the possibility to set up how many points (=pixels) you want to take into account

around the point you are analysing.

For example:

Mask border [pix] = 1 means a square mask of 3 x 3 points around the central one to be filtered. The square mask (of side 2·border+1) is centred at the current pixel

Mask border [pix] = 2 -> 5 x 5 windows

According to the Mask border dimension the filter will have different effects following

detailed

2D pixels of

the Grid 3D points RGB value


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Select one or more Grid point clouds Press the button or Right mouse button Preprocessing

For each grid point cloud a set of filters and computation can be set-up and applied.


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Pre-processing is applied for 2 main purposes:

1) noise removal filter for raw data

2) addition of extra information to raw grid for further processing steps (i.e. registration, meshing, etc.)

3 noise removal filters can be applied to improve Grid quality (n. 1,2,4)

4 options are available for each raw

3 computations can be done to derive and add information to Grid Raw data (n. 3,5,6)


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Filter to remove points according to range distance or reflectance values: Min/Max range [m]: lower/upper threshold of the rangeAll pixels outside this range will be filteredMin/Max reflectance [reflectance value between 0 and 1]All measurements that have an intensity value outside the given interval will be filtered

Filter to smooth the point cloud from local noise roughness.For each point (=pixel) the software assigns the median value calculated using the N point in the square mash centered on the same point.For example Mask border=1 means a 3x3 windows, so the median is calculated according to 9 points. Larger is the Mask border, smoother is the final point cloud

Filter to remove wrong points aligned along the laser ray direction (for example points close to edges – see next slide -, or points viewed from a steep angle, or mixed points from phase shift laser). Defined the laser ray as the vector between the scanner and the acquired point (in red), the software calculates the angle between the laser ray and the vector connecting the center point with each points in the mask. If at list one angle is < the Min incident angle, the acquired point is deleted. Higher is the Mask border, more points will be deleted. Higher is the Min incident angle, more points will be deleted

Laser ray


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Example of mixed points to be filtered: points close to edges


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During the pre-processing it is possible to remove points according to a user defined mask

1. Select a scan and save a 2D image from your scan

2. Edit in black color the

area to delete using any

external software (i.e. Photo Point, Coral Draw, etc.)

3. Run pre-processing: set as Noise

Removal the Mask Filter and assign the

absolute path of your edited image

4. The black points of the

mask will be

automatically delete


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Computes the local surface tangent plane for each point, based on the neighbourhood of the pixel.Smaller is the mask border more local will be the tangent plane calculation.

Filter to computes geometrically significant line features from the grid point cloud. Two types of edges are extracted:- Depth discontinuities (or jump edges) that occur when the scanner hits an occlusion and therefore the measured range jumps from a foreground to a background value.- Orientation discontinuities (or crease edges) that occur when the object has a sudden change of its surface orientation.

Mask border [pix]: the kernel of the filter is a square mask (of side 2·border+1) centred at the current pixel.Min depth discontinuity to flag [m]: set absolute depth discontinuity according to the object scale.Min orientation discontinuity to flag [deg]: the current point is marked if its normal differs from the adjacent ones of at least this angle.

Edge detection results will be used fro Meshing (see Quick Guide n.5 Meshing&MeshEditing)

1. Overview 4. Results3. Computation 5. Contacts2. Noise Removal

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Computes a confidence value for each measurement, which is

a measure for the reliability of the given range measurement.

The accuracy does not only depend on the type of scanner

used, but amongst others also on the following factors:

- incident angle between the laser beam and the tangent plane

of the target

- distance to the target

- material of the object

- intensity of the reflected signal

The confidence value is computed as a weighted sum of the surface normal, the range value and the reflectance value.

Min/Max range [m]: the range is weighted by normalizing it within this interval

Scale factor: the confidence value calculated for each pixel is multiplied with this scale. Thus the user has the possibility to

decrease or increase the weight for a given scan manually, for example because a scanner with higher accuracy has been used

during acquisition.

Weight of range/reflectance/inclination: modify the weight as desired


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The pre-processing can use the multi-processor characteristics of your PC

You can run the pre-processing

from the same scan several times.

If you need to reset the previous

preprocessing effects, switch on the

Use back up option

Run the pre-preprocessing and view the results!


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Is possible to save pre-processing parameters and load them for other scans or projects

The preprocessing

parameters are

saved in a XML file


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View the Pre-processing results: preprocessed scan has the P icon

Noise removal filters are visible

looking in detail the point clouds.

i.e. false mixed points are cleaned

Compute filters add new information layers to the Grid

Inclination Confidence

Edges extraction:

Right button of the mouse on the

Grid filter tool extract edges

Edges can be exported as 3D DXF polylines


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If you need some more information, please contact

our Gexcel Sales Team writing to

[email protected]

Phone (+39) 030 6595001


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mailto:[email protected]

Documents

JRC 3D Reconstructor - Gexcel · Select a scan and save a 2D image from your scan 2. Edit in black color the area to delete using any external software (i.e. Photo Point, Coral Draw,