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Point cloud to NURBS

Point cloud to NURBS is a stand-alone application. This software can fit a NURBS surface to a point cloud by clicking one button. The feature includes:

1. Import point cloud file formatted by .xyz and .txt ;

2. Fit point cloud to a NURBS surface ;

3. Export the surface to .igs file;

4. Controllable fitting precision. The maximum deviation between points and surface can be specified;

5. Controllable surface smoothness. The surface's smoothness can be adjusted by 5 levels;

6. Handle large scale data. Surface control point number can reach 300X300 which enables the program to fit large scale data, e.g terrain model for survey;

7. Easy to use. Just click one button to create surface from point cloud.

 

Tutorial to fit a NURBS surface to a point cloud

Dialog:

After you clicked menu button 'Surface>Point cloud to nurbs' you will see a dialog like the following picture:

Parameters:

  • Pull orientation: pull orientation (dx, dy, dz) is the normal of the fitting plane. The orientation is used as a workspace in the fitting solution. The pull orientation determines the quality of surface. Generally, the program will calculate a optimum pull orientation for surface fitting. However, sometimes it may be bad for some cases.Pull orientation lets user change the orientation (dx, dy, dz) for better surface generation.

  • Control point number: set surface control point in U-direction and V-direction, this control point number will be used as initial number for surface fitting computation. This is optional , program will compute the reasonable surface control point number as default.

  • Surface degree: specify the surface degree in U-direction and V-direction, the default number is U==3 and V==3 , the maximum degree is U==8 and V==8.

  • Max deviation: threshold for the maximum deviation between points and surface. The levels include: no constraint, 0.5, 0.1, 0.0, 0.001, 0.05, 0.3, 1.0, 0.0001;

  • Smoothness: surface smoothness factor, to choose a smoothness level for controlling surface smoothness quality. The levels include: highest, high, medium, low, lowest;

  • Apply: click this button to create a surface that fits the point cloud. After you have fitted a surface successfully, you can choose a more little 'max deviation' number and continue to click this for updating the surface with higher precision.

  • Report: click this button to save the deviation values between every points and surface into a .txt file as report.

 

Tutorial 1. How to fit a NURBS surface to a point cloud


Step 1 : Open the sample file skidoo.xyz . You will see the point cloud model shown as the following picture.

Step 2: Click menu 'Surface->Point cloud to nurbs', the dialog appears. Some parameters for 'Pull orientation' and 'control point number' have been figured out automatically, you can specify new parameter values which you think better or click button 'Apply' directly to create a new surface. After you clicked 'Apply' button, wait for a while, a fitted surface will generate.

The bottom RESURF output message reports that 'Maximum deviation : 0.162620 ; average deviation: 0.018632'. This means that the maximum deviation between points and surface is 0.16262, the average deviation is 0.018632.

View the surface by rotation:

Step 3: Choose Max deviation as 0.1, continue to click Apply button. The surface was updated.

Resurf output message reports the tolerance as the following picture:

The report tells user the maximum deviation between points and surface is 0.084428 which is under the specified threshold 0.1.

 

Step 4: Click button 'report' to save the deviation values as a .txt file. The report file is formatted as "point id, point (x, y, z), projected point on surface (x, y, z), uv value(u, v), deviation distance".

Step 5: Close the dialog. Click menu 'View->mode->Hide mesh' to hide the points, and click menu button 'View->Mode->Show surface CPS' to display surface control point.

Step 6: Click menu 'File->save' to save the surface as .igs file.

 

 

Tutorial 2. Improve the surface by adjusting 'Pull orientation'


Step 1 : Open the sample file expfunctional.xyz . You will see the point cloud model shown as the following picture.

Step 2: Click menu 'Surface->Point cloud to nurbs', the dialog shows. Some parameters for 'Pull orientation' and 'control point number' have been figured out automatically, you can specify new parameter values which you think better or click button 'Apply' directly to create a new surface. After you clicked 'Apply' button, wait for a while, a fitted surface will generate. The following picture is created afte clicking 'Apply' button with default parameter values. However, this surface is not good due to the default 'Pull orientation' vector (0.864, 0.002, -0.503) is not reasonable for this model. After observation on the point cloud model. The best ' Pull orientation' should be (0, 0, 1.0) , so we need to set the ' Pull orientation' to be (0, 0, 1.0) and refit the surface.

Step 3: Set the Pull orientation to be (0, 0, 1.0) (see the following picture), continue to click Apply button. The surface was updated.

The following picture shows the upated surface, it has been improved now.

The program reports the maximum deviation and average deviation in the output message dialog:

Step 4: Close the dialog. Click menu 'View->mode->Hide mesh' to hide the points, and click menu button 'View->Mode->Show surface CPS' to display surface control point.

Step 6: Click menu 'File->save' to save the surface as .igs file.

 

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Standalone application

       Point cloud to NURBS

1.01

 

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