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1、Studio Tutorial Point Cloud Editing Objective Learn to edit a point cloud Use the various sampling functions to reduce the number of points while maintaining the geometric shape Improve the dataset by reducing the noise caused by scanners Use the Wrap operation to polygonize the point cloud Files Ge
2、omagic Studio 6 Tutorial Data latch scan wrp 1 Open latch scan wrp This is scan data of an automotive sheet metal part containing about 900 000 points To create a NURBS surface of this part we must first create a polygon mesh through the points However before doing that there are options available f
3、or reducing both the number of points and the inherent noise of the scan data 2 To be able to rotate around the model more quickly and efficiently go to the Display Panel on the left hand side of the screen and set the Dynamic Display value for points to 25 This means only 25 of the data will be vis
4、ible as we rotate improving rendering speeds 3 First we must clean up the stray points known as outliers that exist around the outside of the part They are usually easy to identify as points that are far away from the main point cloud and do not represent any geometry that we want to keep Outliers t
5、ypically occur when digitizers such as laser scanners inadvertently scan objects in the background such as tabletops walls support structure etc 4 Select Top View from the Views toolbar 5 Zoom in on the line of points visible now on the left side of part shown below 6 Use the Lasso Tool to select on
6、ly these outliers as shown below If you inadvertently select points you do not want to delete simply hold down Ctrl while dragging the Lasso Tool around them to deselect 7 Use the Erase command to delete the selected points You can also use the Delete key on the keyboard Select Ctrl D to fit the mod
7、el to the screen 8 Instead of manually deleting all these outliers we can also let the software detect them automatically From the Edit Select menu choose Disconnected Components Change the Separation dropdown menu to Low and leave the Size value at 5 This function selects clusters of points that ar
8、e separated from the majority of the points Separation indicates how far the clusters can be to the main cloud and still be selected and the Size determines how large the clusters can be Thus we asked the software to select any cluster of points with 5 or less of the total number of points with a re
9、latively low separation from the main cloud 9 Click OK to exit the command Use the Erase command to delete the selected points Notice how all of the stray points have been deleted 10 Before doing anything else click Edit Undo or type Ctrl Z This will restore all of the outlier points Many of the new
10、est functions in Geomagic Studio include the ability to perform multiple operations with one function The Reduce Noise function is one example of that 11 Clear any selected points using Edit Clear All or type Ctrl C The following is a brief explanation of scan noise Frequently during the scanning or
11、 digitizing process an element of noise is introduced into the data Noisy data is identified by a rough uneven appearance in the surface model and is due to such factors as small vibrations in the scanning device inaccurate scanner calibration or poor preparation of the physical object s surface Geo
12、magic has a function called Reduce Noise that helps to minimize the amount of noise present in the scan and thus better represent the true shape of the object Below is a picture of a polygonal model of a typical part before and after the noise reduction process 12 Select Reduce Noise from the Points
13、 menu Choose the Free form Shapes option use the Prismatic Shapes option when you have sharp edges or small details to preserve Set the Smoothness Level to Medium 13 Under Max Displacement toggle on the Limit checkbox and set the Limit to 0 1 mm This option allows the user to limit the movement of d
14、ata points during the smoothing process The user can then choose to either select or delete any points that would have moved more than the specified limit For this example choose the Select Outliers option Also toggle on the Include Isolation Points checkbox This will automatically find and remove d
15、isconnected components or outliers which are very far from the point cloud i e isolated 14 Click Apply to begin the calculation The error in the data caused by the scanner is averaged to produce a smoother surface The Average Distance and Standard Deviation values are reported under Statistics at th
16、e bottom of the dialog box Quick Tip This function is best run on larger data sets i e before doing any sampling 15 Notice that some points are red or selected These represent the outliers points that are far away from the main point cloud or points that would have had to move more than 0 1 mm during the smoothing process It is safe to assume these may have been erroneous points resulting from perhaps improper surface coating or an uncalibrated digitizer In fact you can even see in the image at
