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mesh_tessellation.md

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Generation of a point cloud with uniform density using MeshLab:

  1. Scale the point cloud to the correct units (meters)

    • Render -> Show box corners
      • To see the range in XYZ of the mesh (to confirm if it is in mm, cm, m, ...)
    • Filters -> Normals, curvatures and Orientation -> Transform: Scale, Normalize
      • To make uniform scaling (0.001 in XYZ to change from mm to m)

  2. Preprocess the mesh to ensure that the meshlab algorithms work correctly:

    • Filters -> Cleaning and Repairing -> Remove Faces from Non Manifold Edges
    • Filters -> Normals, curvatures and Orientation -> Normalize Vertex Normals

  3. Increase the density of triangles using either:

    1. Mid point Subdivision and subsampling
      • Achieves better accuracy since the generated mesh triangles are on the same surface of their original triangles (uses subdivision)
      • Mid point division usually does not achieve uniform point density, requiring a subsampling algorithm that loses mesh information and generates a point cloud
      • Mid point Subdivision
        • Filters -> Remeshing, Simplification and Reconstruction -> Subdivision Surfaces: Midpoint
          • Iterations: 100
          • Edge Threshold (world unit): 0.002 m (for example, but can be + or - depending on the size of the part and the desired accuracy)
      • Subsampling of the mesh for having +- an uniform density of points using either:
        1. Poisson-disk Sampling (preferred method since it creates points in the middle of the triangles using a Poison distribution)
          • Filters -> Sampling -> Poisson-disk Sampling
        2. Filters -> Sampling -> Clustered Vertex Subsampling
        3. Filters -> Point Set -> Point Cloud Simplification
    2. Uniform Mesh Resampling
      • Achieves better point density uniformity and keeps the mesh information
      • May generate artifacts which cause the generated mesh surface to diverge slightly from the original mesh
      • Filters -> Remeshing, Simplification and Reconstruction -> Uniform Mesh Resampling
        • Precision (world unit): 0.002 m (for example, but can be + or - depending on the size of the part and the desired accuracy)
        • Clean vertices

  4. Post processing

    • View -> Show Layer Dialog
    • Hide the original mesh
    • Select the view of the mesh and then the points to confirm that the generate mesh / point cloud is adequate
    • Render -> Show Normal -> For confirming that there are normals for the point cloud and they are correct
    • Filters -> Normals, curvatures and Orientation -> Normalize Vertex Normals

  5. Export

    • File -> Export Mesh As
      • .ply
      • Save Vert Normal
      • Binary encoding