Creating a Polygonal Mesh using IMMerge – Polyworks V11

This series will show you advanced modeling building modeling techniques using Leica’s Cyclone.
Hint: You can click on any image to see a larger version.

As objects become more complex, using layers (Shift + L) becomes essential to organizing and controlling the model space.

Once a point cloud data set has been properly aligned with overlap reduction, it is ready for meshing. IMMerge is the module in Polyworks that creates a mesh from an IMAlign project. Note – Only IMAlign projects can be meshed. See below for specifics for IMMerge operations.

BASIC SETTINGS

In the Polyworks Workspace Manager, select the IMAlign project that you want to mesh and then select Create a Polygonal Model in the Workspace Manager.

IMMerge – Basic Settings

Values Carried over from IMAlign Project (usually do not change)

Max Distance: The maximum distance between two overlapping scans
Surface Sampling Step: Average of interpolation step across scans; the resulting mesh
density
Standard Deviation:
Approximate alignment error (In meters for Optech)

Smoothing Level: Can be modified. It is generally recommended to have Low to Med level of
smoothing.

ADVANCED SETTINGS

Advanced Settings Explained – (usually do not change)

Reduction Tolerance:
- Compresses the mesh by reducing the number of triangles (without loosing definition)
- Typical Reduction Tolerance = 1/5 * max standard deviation

Smoothing Radius
- Radius of the spherical filter used to smooth the resultant mesh.
- The greater the smoothing radius, the more the mesh is smoothed.
- Typical Smoothing Radius: 2-4 times the surface sampling step

Smoothing Tolerance
-
Typical Smoothing Tolerance: 3 x’s max standard deviation

Common Error returned from IMMerge processing of very large datasets
Error 1413:
Block Size too small or Out of memory

- Actually not a function of block size, so DO NOT increase block size. Recommended block size and compaction is 200 and 20, respectively. Instead, change the subdivision settings. Change the “# of triangles per job” to “# of Merging jobs” and where it says default, set a value. Start at 1000 then double if the operation still does not merge. If it does not merge in 10000 jobs or less, then the dataset is probably too large.

- If the dataset will not merge, split the IMAlign project into two pieces and mesh the two pieces separately.

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