1. dia

1
Óbuda University John von Neumann Faculty of
Informatics Institute of Applied Mathematics
Course Introduction to virtual engineering
Lecture and laboratory 7. Processing point
clouds into surfaces
László Horváth university professor
http//users.nik.uni-obuda.hu/lhorvath/
2
Contents

Lecture
Reverse engineering for the definition of surface
using measured points .
Creation clouds of measured points.
Principles and methods for the processing of
clouds
Laboratory
Creating curves (VE7.1)
Editing and filtering clouds of points (VE7.2)
Projecting curve to cloud (VE7.3)
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
3
Reverse engineering for the definition of surface
using measured points
Physical shape
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
4
Activating a portion of a cloud of points
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
5
Homogeneous filtering
The sphere passes over the cloud of points. All
the points that are inside the sphere are then
hidden or deleted.
.
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
6
Adaptive filtering
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
7
Mesh a cloud of points
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
8
Curve projection to a cloud of points
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
9
Definition of scan and curve in planar section
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
10
Definition of scan and curve in planar section
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
11
Definition of multi-sections surface using a set
of scan originated curves
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
12
Finding free edges on a cloud of points
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
13
Creation clouds of measured points by coordinate
measuring
A contact method Relatively slow. Industrial
automation conform.
Coordinate measuring machine (CMM) A probe
touches object's surface at discrete points under
the control of a computer using measurement
program
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
14
Creation clouds of measured points by 3D scanning
Purpose Non-contact methods for the collection of
distance (points on shape) and appearance (color)
information on physical objects.
Objective Reconstruction of a shape with
application defined accuracy
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
15
Several methods for 3D scanning
Active
Passive
Time-of-flight Laser rangefinder distance to the
first object on its path is measured. Laser
emits a pulse of light. Detector reflected light
is seen. Timing the round-trip time of a pulse
of light.
Stereoscopic Human stereoscopic vision
based. Two video cameras are arranged. Differences
between the images seen by each
camera. Determine the distance at each point in
the images.
Triangulation Laser on the object A camera looks
for the location of the laser dot. Laser dot,
camera and laser emitter form a triangle.
Photometric Single camera Multiple images under
varying lighting conditions. Surface orientation
at each pixel.
Handheld Laser A laser dot or line is projected
onto an object. Handheld laser device and a
sensor is applied. Position of the scanner is
recorded (laser tracker).
Silhouette Photos are taken around an object
against a background. Outlines created from a
sequence of photos. Silhouettes are extruded and
intersected. Visual hull approximation of the
object. Some concavities are not detected.
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
16
Examples for 3D scanners (1/4)
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
17
Examples for 3D scanners (2/4)
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
18
Examples for 3D scanners (3/4)
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
19
Examples for 3D scanners (4/4)
3D scanning system for Stanford University for
the Digital Michelangelo Project. The Large
Statue Scanner was designed specifically for use
in Italy to digitize many of the works of
Michelangelo. The scanner head consists of a
laser, a range camera, a fiber-optic white light
source, and a high-resolution color camera.
Source www.cyberware.com
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
20
Digitalizing path of human hand move
Freestyle Sketch Tracing Free form model from
online sketch and images. 3D sketch positioning
and trimming. Scale and stretch adjustment at
model generation.
Source http//www.3ds.com/products/catia/catia-di
scovery/
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
21
Definition of surface using cloud of points and
curves
Source www.catia.com
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
22
Creating curves
Laboratory task VE7.1
Definition 3D curve on a series of points.
Creating a series of curves.
Activating portion, selecting points for
processing.
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
23
Editing and filtering clouds of points
Laboratory task VE7.2
Selecting points for processing.
Homogenous filtering, application of sphere.
Adaptive filtering on the basis of distance.
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/
24
Projecting curve to cloud
Laboratory task VE7.3
Projecting curves onto a cloud.
Modification of direction.
Application of discretized input curve for
projection.
László Horváth ÓU-IAM
http//users.nik.uni-obuda.hu/lhorvath/