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The proposed method can be divided into two parts: Triangulation of laserscanner data

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The proposed method can be divided into two parts: Triangulation of laserscanner data

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  1. Triangulation and Smoothing of Terrestrial Laserscanner Dataset by Using Method of Point Projection from 3D Space to 2DJan Řezníček, Karel Pavelka (tutor)Czech Technical University in Prague, Laboratory of Photogrammetrye-mail: jan.reznicek.1@fsv.cvut.czThis research has been supported by the Czech Ministry of Educationgrant MSM No. 34-07401GEOS 2008

  2. GEOS 2008 conference • Triangulation of the point cloud in 3D space can not bring good results, because the algorithm doesn‘t follow the real shape of the object. • Some software (Inus Rapidform, Polyworks) do the triangulation in 2D space using orthogonal projection (in the direction of the screen). This type of triangulation can be used only on a very small parts of the scan due to the overlap effect. • Above mentioned approaches results very often in irregular mesh with a lot‘s of holes, “sliver” and overlap triangles, and other discontinuities.

  3. GEOS 2008 conference The proposed method can be divided into two parts: • Triangulation of laserscanner data • Smoothing of laserscanner data

  4. GEOS 2008 conference Triangulation of laserscanner data • Projection of the point cloud from 3D space to the plane (Cylindrical projection). • Projection from 3D space to cylinder. • Unroll of the cylinder to the plane.

  5. GEOS 2008 conference Triangulation of laserscanner data • Delaunay triangulation in plane (we use Qhull library [1]). Delaunay triangulation maximize the minimum angle of all the angles of the triangles.

  6. GEOS 2008 conference Triangulation of laserscanner data • All vertex are than reprojected back to the original coordinates. The visible “sliver”triangles on the right picture are easy to remove. • The noise in the laserscanner data is about 3–5 mm. Despite of the noise, the mesh keeps its continuity and all triangles are well conected and ready to be smoothed.

  7. GEOS 2008 conference Smoothing of laserscanner data • The smoothing of the mesh is done by simple averaging (which is least square method) the neighbours vertex (points). • The smoothing algorithm is improved with the use of the aditional parameter. This parameter sets the maximum lenght of the triangle to be used for smoothing the neighbour vertex. Than the edge points of the object do not move along “sliver”triangles.

  8. GEOS 2008 conference The final smoothed mesh without „sliver“ triangles.

  9. GEOS 2008 conference The final mesh is very continuous and regular, without any holes inside the measured area.

  10. GEOS 2008 conference The original sculpture named “Onufrius” from town Kuks, carved by Matyáš Bernard Braun in 17th century.

  11. GEOS 2008 conference Software in Java programming language The code was rewritten from Matlab code by Mr. Jiří Mlavec (CTU in Prague).

  12. GEOS 2008 conference Thank you for your attention [1] Documentation of Qhull library, <http://www.qhull.org>.

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