3D Printing

CONTENTS

• INTRODUCTION

• 3D SENSING DEVICES

• 3D SENSING WITH KINECT

• 3D MODEL RECONSTRUCTION

• KINECT FUSION

• 3D PRINTER

• SYSTEM ARCHITECTURE

• 3D PRINTING

• CONCLUSION & FUTURE SCOPE2

INTRODUCTION

• From sense to print system:

• System that generates ready-to-print 3D models of

objects.

• It doesn’t require manual intervention the processing.

• These 3D models generated resemble and emulate the

real world.

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• Steps in creating a 3D model :

• Segmentation

• Triangulation

• Scaling of the object to the dimension of the 3D printer

• Main components of system:

• 3D sensing device connected to the cloud

• Model reconstruction device to generate 3D CAD models

• 3D printers5

INTRODUCTION

3D SENSING DEVICES

• Generates 3D representations of the object using a

sensor.

• Generally in the form of 3D point clouds.

• 3D point clouds are generated from depth images.

• In depth image each pixel has a depth value assigned to

it.

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• Depth values: Distances of surfaces in the world to the

origin of camera

• Common approaches for acquisition of depth images are:

Time of flight(TOF) systems

Triangulation based systems

Kinect sensor based systems

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3D SENSING DEVICES

• TOF systems :

• The systems that emit signals like light.

• It then measure the time taken for the signal to

bounce back.

• Examples : LIDAR , radars etc

• Triangulation based systems:

• Measures distances to surfaces by matching

correspondences viewed by two sensors.

• Example: multi camera stereo vision system 7

3D SENSING DEVICES

• Kinect sensor based systems are:

• Monochrome CMOS sensors combined with laser

projector.

• The technology is called light coding.

• It is a variant of image based 3D reconstruction.

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3D SENSING DEVICES

3D SENSING WITH KINECT

• This technique make use of the Kinect sensor.

• Kinect is a cheap and accessible 3D sensor.

• Uses light coding technique.

• Developed by Microsoft

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3D SENSING WITH KINECT

• It has one camera and one IR projector

• Principle of light coding:

• Project a known IR pattern on to the screen

• Depth information is acquired from this pattern.

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IR ProjectorCamera IR Camera

3D SENSING WITH KINECT

• IR Patterns from a Kinect Sensor (can only be viewed

only in a night vision camera)

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3D MODEL RECONSTRUCTION

• Model Reconstruction is done by taking multiple views.

• These are obtained by moving the 3D sensing device

around the object.

• A full set of 3600 views are taken.

• Registering these multiple views will develop the full

3D model.

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3D MODEL RECONSTRUCTION

• Registration : Estimation of rigid motion of a set of

points w.r.t another set of points.

• A set of points are transformed into a surface using mesh

algorithms

• Popular mesh algorithms are:

Greedy triangulation

Marching cubes

Poisson reconstruction13

RECONSTRUCTION – MARCHING CUBES

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• The 3D points from the sensor is divied into number

of cubes.

• Each cube will intersect the surface in different

manners.

• This algorithm determines how the surface intersects

each cubes.

• There are 15 possible ways of intersecting the cube.

RECONSTRUCTION – MARCHING CUBES

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• Creates a triangular mesh from the intersections in one of

the several cubes.

• Calculates the normals to the surface at each vertex of the

triangle.

• Then it marches to the next cube and repeat the above

process.

3D PRINTERS

• 3D objects are created using layering techniques.

• 3D printing technologies include:

Stereo lithography

Fused deposition modeling (FDM)

• FDM is popular in commercial 3D printers.

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SYSTEM ARCHITECTURE

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3D PRINTING

• Here printing is based on the following assumptions

• Scanned object, an inanimate object or human is

standing, sitting or lying on a plane

• 3D sensing device must close a loop around this

object

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• Two ways of printing a 3D human are:

Full body statue

Bust

• To print a bust we concentrate on:

Face and head

There is no ground plane

• Camera poses tells us whether the human is sitting or

standing upright

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3D PRINTING

• After applying segmentation and scaling, a polygon

mesh is generated.

• The resulting file is automatically sent to the machine

on the network.

• The machine is connected to the 3D printer.

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3D PRINTING

FLOW OF 3D PRINTING FROM

3D SENSING DEVICE

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CONCLUSION & FUTURE WORKS

• From Sense to Print is a system that can automatically generate

ready-to-print 3D CAD models.

• It uses low-cost Kinect sensor.

• It automatically scales the reconstruction to the size of the 3D

printer.

• The 3D prints currently generated are full models.

• Works are progressing on an automatic approach to generate the 3D

shells.

• They create replicas in more expensive materials such as copper or

other metals. 22

REFERENCES

• R. A. Newcombe, S. Izadi, O. Hilliges, D. Molyneaux, D.

Kim, A. J. Davison, P. Kohli, J. Shotton, S. Hodges, and A. W.

Fitzgibbon, “Kinect- fusion: Real-time dense surface mapping

and tracking.”

• R. Rusu and S. Cousins, “3d is here: Point cloud library

(PCL)”

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