Meshes are the final result of processing a scan or cloud and are the basis upon which most data extraction is performed. The mesh structure itself is a set of vertices and a set of edges and faces that connect those vertices as well as any color or intensity values that were in the cloud or scan that the Mesh was created from.
One can import a .tin file simply by right-clicking the Meshes folder and selecting Import and navigating to the .tin on disk.
There are several methods for creating a mesh, but all of these methods use one of two cloud creation dialogs. The most common and direct method of creating a mesh is to right click the source data object (either another mesh, a cloud or a scan) and select Create ⇒ Mesh. You can also access the Create Mesh dialog form the Action Tab. Creating a mesh from another mesh will re-triangulate the points in that mesh based on the new normal information provided in the Create Mesh dialog, so it is entirely possibly that your new mesh can look completely different.
This dialog operates in two different modes: multiple source mode and single source mode. The single source mode is typically the result of right-clicking a data object in the PointCloud tree structure and selecting Create Mesh or from the Action Tab, this mode only allows the mesh to use the originally selected data as its source. Use filters determines whether or not to filter out vertices based on any filters applied to the source object. The Normal is the direction to use for the Delaunay mesh triangulation; typically you want to use an axis that is representative of the direction that the data was taken from, such as the view direction of the scanner. In the case of scans, there will be a From Scan radio button that you can use, which will automatically use the scanner position information from the scan as the normal. The Mesh Faces panel allows you to set restrictions on the meshing process. No edge in the mesh will be created if it will exceed the Maximum edge length or if the angle between the two faces it connects exceeds the Maximum incident angle. Mesh Vertex Limits specify the maximum number of mesh vertices that will be used in a mesh. Setting this value too low may result in no mesh being created. One can also create a mesh with multiple sources by right-clicking the Meshes folder and selecting Add ⇒ New, this will bring up a dialog similar to the one above with an extra tree control to the left.
All of the controls on the right half of the dialog are the same, but you can now toggle inclusion of objects into the mesh by clicking the red x next to their name in the tree, turning the icon to a green circle.
The Smooth Mesh command allow you to create a new mesh or modify the existing mesh. There are two methods for smoothing. They may be used separately or in combination.
Smooth Spikes applies the user values for the parameters to remove or reduce the number and severity of spikes in the selected mesh.
Average
- Spike Slope % is the angle in degrees of the profile slope required for a vertex to be considered a spike. a value of 90% will disable this test.
- SD Threshold is the distance from the average plane based on the surrounding points that qualifies a vertex as a spike.
- Min Radius is the distance to from a point to look for the surrounding points.
- Point Adjustment Factor is how far a point should be moved to bring it into the average plane. 0 is no movement. 1 is complete movement.
- Passes: Value 1-9. This is the number of times the process should be run.
- Use Max Length This is an alternative to the Minimum Radius option and should only be used is there are a significant number of breaklines in the mesh.
- Factor is how far a point should be moved to bring it into the average plane. 0 is no movement. 1 is complete movement.
- Passes Value 1-9. This is the number of times the process should be run.
- Steps is the number of vertices to step out from the current vertex when calculating the average.
- Minimum Distance is the minimum distance a point must be moved to be smoothed. If the point would be moved less than this value it is left and not moved.
Simplifying a mesh is one of the key ways to reduce data down to a state that it can be transferred over to CAD software or to make it more manageable in PointCloud without losing much surface quality. Right-click the mesh to simplify and select Simplify. This will open the Simplify Mesh dialog.
There are two methods of mesh simplification available. The Elevation Difference method will loop over all the vertices in the mesh Passes number of times and each vertex whose deletion would lead to a deviation in the mesh of less than the Threshold will be deleted. Elevation Difference is generally slower. The Edge Cost method determines the total deviation in the mesh that result from each edge removal (by merging its two vertices) and removes all edges whose removal would result in a deviation of less than the Threshold. In addition, the preserve breaklines options for the Edge Cost method will multiply the deviation value calculated by the Breakline Weight if the angle between the two faces it borders is greater than the Breakline Angle, this can be used to help preserve corners. The Elevation Difference method is best used in largely flat data (such as a scan of a large open area), while the Edge Cost method is best for complex data with lots of corners. Additionally there is a memory tradeoff, the Elevation Difference method is generally slower at higher numbers of passes (which gives better results), while the Edge Cost method consumes more memory.
To remove spikes from a mesh, right-click the target mesh and select Clean.
Vertices that meet the parameters of this dialog will have their positions adjusted to meet the shape of the vertices around them, smoothing out the mesh. These parameters are as follows:
Search Distance determines the distance for a vertex to search for vertices that exceed the Delta % Slope.
Delta % Slope is the maximum change is slope that is allowed. Vertices that exceed this value are removed.
Passes determines the number of passes to make over the mesh.
Resampling a mesh goes through the list of points in a Mesh and
takes one out of each "Step Value" points. Therefore the number of points in
the resulting Mesh will be (1 / Step Size) times the original
number of points in the Mesh.
To run this command, right-click on the existing mesh and select Resample.
Original Mesh | Mesh Resampled Step
2 |
Mesh Resampled Step
10 |
Approximate File Sizes
of Exported TIN |
||
10Mb |
5Mb |
1Mb |
Tab Location(s): Project Tab
Tree Folder: Meshes
Prerequisite: An Existing Mesh