mesh

Generate isosurface mesh from active voxels

Since R2024b

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    Syntax

    [vertices,faces] = mesh(sdm3D)

    Description

    [vertices,faces] = mesh(sdm3D) uses the Marching Cubes algorithm to generate an isosurface mesh from active voxels that define the zero-level set.

    example

    Examples

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    Open Live Script

    Read and plot the triangulation data from the L-membrane STL. You can use this to compare with the signed distance map.

    triL = stlread("L-Membrane.stl");
trisurf(triL)
title("L-Membrane STL")
[az,el] = view;
axis equal

    Figure contains an axes object. The axes object with title L-Membrane STL contains an object of type patch.

    Create an empty 3-D signed distance field (SDF) and load the point cloud data for the L-membrane from a MAT file. The MAT file contains point cloud data and the sensor origin associated with each point cloud data.

    sdm3D = signedDistanceMap3D(Resolution=50);
load LMembranePC.mat

    Insert each point cloud into the signed distance field and show the updated 3-D SDF.

    for i = 1:size(ptcloud,1)
    insertPointCloud(sdm3D,origin(i,:),ptcloud{i});
    show(sdm3D,Colorbar="on");
    view(az,el)
    axis equal
    drawnow
    pause(.25)
end
title(["3-D SDF of L-Membrane"])

    Figure contains an axes object. The axes object with title 3-D SDF of L-Membrane contains an object of type scatter.

    Get all active voxels in the 3-D SDF.

    vox = activeVoxels(sdm3D)
    vox = struct with fields:
           ID: 1
      Centers: [49889×3 double]
    Distances: [49889×1 double]
        Sizes: [49889×1 double]

    For demonstrative purposes, use a random xyz-offset from the voxel centers of the first three voxels as query points. Then get the distance and gradient using those query points.

    querypts = vox.Centers(1:3,:) + 0.1*rand(3,3);
d = distance(sdm3D,querypts)
    d = 3×1

    0.0379
   -0.0447
    0.0600


    g = gradient(sdm3D,querypts)
    g = 3×3

    0.1924    1.5773   -1.4002
    0.1689    1.6524   -0.8267
   -0.0715   -0.2335    0.3677

    Generate a mesh from the 3-D signed distance field.

    [vertices,faces] = mesh(sdm3D)
    vertices = 18860×3

   -0.0100    0.0068    0.1500
   -0.0300    0.0059    0.1500
   -0.0100    0.0100    0.1610
   -0.0300    0.0100    0.1565
    0.0100    0.0047    0.1500
   -0.0100   -0.0100    0.1409
    0.0100   -0.0100    0.1421
    0.0100    0.0025    0.1700
   -0.0010    0.0100    0.1700
    0.0100    0.0094    0.1900
    0.0089    0.0100    0.1900
    0.0100    0.0100    0.1909
   -0.0100    0.0187    0.1700
   -0.0300    0.0259    0.1700
   -0.0100    0.0552    0.1500
      ⋮


    faces = 37094×3

     2     1     3
     4     2     3
     7     1     6
     5     1     7
     9     3     1
     9     1     8
     8     1     5
     8    10    11
     9     8    11
    10    12    11
     3    14     4
    13    14     3
    15    16    17
    16    18    17
     9    13     3
      ⋮

    Visualize the mesh data.

    meshTri = triangulation(faces,vertices);
trisurf(meshTri)
axis equal
title("Mesh from 3-D SDF")

    Figure contains an axes object. The axes object with title Mesh from 3-D SDF contains an object of type patch.

    If needed, you can use this mesh data to create a collision mesh using V-HACD. See collisionVHACD (Robotics System Toolbox) for more information.

    Input Arguments

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    3-D signed distance map, specified as a signedDistanceMap3D object.

    Output Arguments

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    Generated isosurface mesh vertices, returned as a V-by-3 matrix. Each row represents an xyz-position.

    Generated isosurface mesh faces, returned as a F-by-3 matrix. Each row is triangular face made from three vertices. Each element is an index corresponding a vertex in the vertices argument.

    Extended Capabilities

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    C/C++ Code Generation
    Generate C and C++ code using MATLAB® Coder™.

    Version History

    Introduced in R2024b

    See Also

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