07-07-2014, 04:18 PM
TELE-GRAFFITI
[attachment=65705]
ABSTRACT
Tele-graffiti is a technology that allows two or more users to communicate remotely via hand-drawn sketches. What one person writes at one site is captured by a video camera, transmitted to the other site and displayed there using an LCD projector.
The system was developed at Robotics Institute of Carnegie Mellon University, Pittsburgh. The system comprises of a digital camera, a high resolution LCD projector to project the received image, a mirror to reflect the projected image onto the paper, fixture to hold these devices in position and a writing pad to fix the sheet of paper on the top of the table at every station.
The user can write on a regular piece of paper with a pen at his desk. The sketch or writing on the paper is captured by the camera and transmits the digitized image to the receiving end through a data link.
The image can be transmitted over the internet or local area network. The software architecture of system runs on Linux and has four threads the drawing thread, the paper tracking thread, sending thread and receiving thread.
Tele-graffiti has various applications. It can play an important role in remote education and remote designing.
It can also serve as a substitute for internet chat. The advantage of the system is that non-computer people can use it.
INTRODUCTION
Tele-graffiti is a technology that allows two or more users to communicate remotely via hand-drawn sketches. What one person writes at one site is captured by a video camera, transmitted to the other site and displayed there using an LCD projector.
The system was developed at Robotics Institute of Carnegie Mellon University, Pittsburgh. The system comprises of a digital camera, a high resolution LCD projector to project the received image, a mirror to reflect the projected image onto the paper, fixture to hold these devices in position and a writing pad to fix the sheet of paper on the top of the table at every station.
The user can write on a regular piece of paper with a pen at his desk. The sketch or writing on the paper is captured by the camera and transmits the digitized image to the receiving end through a data link.
The image can be transmitted over the internet or local area network. The software architecture of system runs on Linux and has four threads the drawing thread, the paper tracking thread, sending thread and receiving thread.
Tele-graffiti has various applications. It can play an important role in remote education and remote designing.
It can also serve as a substitute for internet chat. The advantage of the system is that non-computer people can use it
Tele-Graffiti is a remote sketching system that we have recently developed [Takao et al., 2001] [Baker and Shi, 2002] [Takao et al., 2002]. Although the Xerox “Double Digital Desk" [Wellner, 1993] is an elegant idea; there are a number of technical problems that need to be Solved to make it practical and usable:
HARDWARE SPECIFICATIONS AND SETUP
Example Tele-Graffiti systems. We have created 2 different prototypes. (a) The projector is mounted horizontally on a supporting plate. (b) The projector is mounted vertically on the pillar of the stand. Prototype 2 was largely designed by Iain Matthews.
PC:
Each Tele-Graffiti site has a PC with dual 450MHz PentiumII processors, an “ NVidia GeForce2 GTS" video card, and an OrangeLink Firewire (IEEE1394) card. We use these cards because they have good XWindow/OpenGL support under Linux.
Adjusting the Stand
The Tele-GraÆti stands are highly configurable. The mirror, camera, and projector each have 2 degrees of freedom. The mirror can be rotated and moved inwards and outwards. The camera can be rotated and also moved inwards and outwards. The projector can be rotated and moved up and down. To set up the stand, the following two operations have to be performed:
Adjust the Projected Area:
Set up the projector so that it is projecting a constant color, typically blue. Adjust the mirror and the projector so that the projector projects light entirely onto the mirror and the light is rejected approximately vertically downwards to create an approximately rectangular region on the desktop. Keystone correction can be used if so desired to make the working area more rectangular.
Adjust the Viewable Area:
Move and rotate the camera so that the center of the captured image is approximately the same as the center of the image projected by the projector. To help in this task, we use a program that displays a “cross" in the center of the projected image.
TELE – GRAFFITI SYSTEM SOFTWARE
Each Tele-Graffiti site needs to continuously capture video from its camera, track the paper
in the video, warp the image to display so that it is aligned with the paper, and communicate with the other sites. In this section we describe the system software that performs all of these tasks. We begin by describing the system architecture and the 4 threads that it consists of. We then detail each of the 4 threads in turn. We conclude this section by describing the run-time performance of the system
Drawing Thread
This thread continuously warps and draws the image to display. The drawn image is output to the projector simply by plugging the monitor output of the PC into the projector. Dual headed video card could be used instead. The Drawing thread waits for updates to the image to display and upon update copies the new image into the OpenGL texture buffer. This thread also waits for changes to the local paper vertices. Whenever this occurs, the Drawing thread redraws (re-maps) the texture on the screen with the new local paper vertices.
ADVANTAGES
The advantage of this system is that the occlusions caused by the user’s hands and the distractions caused by printed or hand-written material on the paper are overcame by using a algorithm that takes advantage of the facts that (a) the paper is bounded by four long edges roughly perpendicular to each other, (b) we know the approximate location of the projected image from the previous time-step and therefore its edges can be removed, and © the asymmetry between the top and the bottom of the clipboard can be used to resolve the ambiguity in the paper orientation.. In Tele-Graffiti, paper detection and tracking is based on real-time paper boundary detection
APPLICATIONS
Real –Time Paper Tracking and Video Transmission:
We have developed a real-time paper tracking algorithm that allows the users of Tele-Graffiti to move the paper during operation of the system. The result is a much more versatile system. We have also developed software architecture for Tele-Graffiti and implemented real-time video transmission over IP networks on a standard 450MHz PCs.
Hand-Based User Interface and Automatic Summarization:
We have added a user interface to a Tele-Graffiti based on hand-tracking .The system requires no extra hardware, and operates with the Tele-Graffiti cameras. Infra-red cameras are not required. The user interface detects when the user has their hand over the paper and processes their interaction with user interface objects such as buttons and sliders. We have also developed an automatic summarization system for Tele-Graffiti based on detecting when the users have their hands over the paper. Such a system can automatically summarize a several minute long sketching session into a few 10's of frame.
Feedback Analysis for Gain Selection and Image Separation:
We have analyzed the Tele-Graffiti feedback loop and derived the final steady state that the system converges to. We use this analysis to derive the optimal gain with which to set up the system to maximize the image quality; to minimize visual echoing, but to maximize how well the sketch from the other site is visible. We extended this analysis to Tele-Graffiti running with automatic gain control (AGC) and colour images. We have also derived an algorithm to separate the two final viewed images (which are a weighted combination of the two sketches at the two sites) into the two component sketches.
[attachment=65705]
ABSTRACT
Tele-graffiti is a technology that allows two or more users to communicate remotely via hand-drawn sketches. What one person writes at one site is captured by a video camera, transmitted to the other site and displayed there using an LCD projector.
The system was developed at Robotics Institute of Carnegie Mellon University, Pittsburgh. The system comprises of a digital camera, a high resolution LCD projector to project the received image, a mirror to reflect the projected image onto the paper, fixture to hold these devices in position and a writing pad to fix the sheet of paper on the top of the table at every station.
The user can write on a regular piece of paper with a pen at his desk. The sketch or writing on the paper is captured by the camera and transmits the digitized image to the receiving end through a data link.
The image can be transmitted over the internet or local area network. The software architecture of system runs on Linux and has four threads the drawing thread, the paper tracking thread, sending thread and receiving thread.
Tele-graffiti has various applications. It can play an important role in remote education and remote designing.
It can also serve as a substitute for internet chat. The advantage of the system is that non-computer people can use it.
INTRODUCTION
Tele-graffiti is a technology that allows two or more users to communicate remotely via hand-drawn sketches. What one person writes at one site is captured by a video camera, transmitted to the other site and displayed there using an LCD projector.
The system was developed at Robotics Institute of Carnegie Mellon University, Pittsburgh. The system comprises of a digital camera, a high resolution LCD projector to project the received image, a mirror to reflect the projected image onto the paper, fixture to hold these devices in position and a writing pad to fix the sheet of paper on the top of the table at every station.
The user can write on a regular piece of paper with a pen at his desk. The sketch or writing on the paper is captured by the camera and transmits the digitized image to the receiving end through a data link.
The image can be transmitted over the internet or local area network. The software architecture of system runs on Linux and has four threads the drawing thread, the paper tracking thread, sending thread and receiving thread.
Tele-graffiti has various applications. It can play an important role in remote education and remote designing.
It can also serve as a substitute for internet chat. The advantage of the system is that non-computer people can use it
Tele-Graffiti is a remote sketching system that we have recently developed [Takao et al., 2001] [Baker and Shi, 2002] [Takao et al., 2002]. Although the Xerox “Double Digital Desk" [Wellner, 1993] is an elegant idea; there are a number of technical problems that need to be Solved to make it practical and usable:
HARDWARE SPECIFICATIONS AND SETUP
Example Tele-Graffiti systems. We have created 2 different prototypes. (a) The projector is mounted horizontally on a supporting plate. (b) The projector is mounted vertically on the pillar of the stand. Prototype 2 was largely designed by Iain Matthews.
PC:
Each Tele-Graffiti site has a PC with dual 450MHz PentiumII processors, an “ NVidia GeForce2 GTS" video card, and an OrangeLink Firewire (IEEE1394) card. We use these cards because they have good XWindow/OpenGL support under Linux.
Adjusting the Stand
The Tele-GraÆti stands are highly configurable. The mirror, camera, and projector each have 2 degrees of freedom. The mirror can be rotated and moved inwards and outwards. The camera can be rotated and also moved inwards and outwards. The projector can be rotated and moved up and down. To set up the stand, the following two operations have to be performed:
Adjust the Projected Area:
Set up the projector so that it is projecting a constant color, typically blue. Adjust the mirror and the projector so that the projector projects light entirely onto the mirror and the light is rejected approximately vertically downwards to create an approximately rectangular region on the desktop. Keystone correction can be used if so desired to make the working area more rectangular.
Adjust the Viewable Area:
Move and rotate the camera so that the center of the captured image is approximately the same as the center of the image projected by the projector. To help in this task, we use a program that displays a “cross" in the center of the projected image.
TELE – GRAFFITI SYSTEM SOFTWARE
Each Tele-Graffiti site needs to continuously capture video from its camera, track the paper
in the video, warp the image to display so that it is aligned with the paper, and communicate with the other sites. In this section we describe the system software that performs all of these tasks. We begin by describing the system architecture and the 4 threads that it consists of. We then detail each of the 4 threads in turn. We conclude this section by describing the run-time performance of the system
Drawing Thread
This thread continuously warps and draws the image to display. The drawn image is output to the projector simply by plugging the monitor output of the PC into the projector. Dual headed video card could be used instead. The Drawing thread waits for updates to the image to display and upon update copies the new image into the OpenGL texture buffer. This thread also waits for changes to the local paper vertices. Whenever this occurs, the Drawing thread redraws (re-maps) the texture on the screen with the new local paper vertices.
ADVANTAGES
The advantage of this system is that the occlusions caused by the user’s hands and the distractions caused by printed or hand-written material on the paper are overcame by using a algorithm that takes advantage of the facts that (a) the paper is bounded by four long edges roughly perpendicular to each other, (b) we know the approximate location of the projected image from the previous time-step and therefore its edges can be removed, and © the asymmetry between the top and the bottom of the clipboard can be used to resolve the ambiguity in the paper orientation.. In Tele-Graffiti, paper detection and tracking is based on real-time paper boundary detection
APPLICATIONS
Real –Time Paper Tracking and Video Transmission:
We have developed a real-time paper tracking algorithm that allows the users of Tele-Graffiti to move the paper during operation of the system. The result is a much more versatile system. We have also developed software architecture for Tele-Graffiti and implemented real-time video transmission over IP networks on a standard 450MHz PCs.
Hand-Based User Interface and Automatic Summarization:
We have added a user interface to a Tele-Graffiti based on hand-tracking .The system requires no extra hardware, and operates with the Tele-Graffiti cameras. Infra-red cameras are not required. The user interface detects when the user has their hand over the paper and processes their interaction with user interface objects such as buttons and sliders. We have also developed an automatic summarization system for Tele-Graffiti based on detecting when the users have their hands over the paper. Such a system can automatically summarize a several minute long sketching session into a few 10's of frame.
Feedback Analysis for Gain Selection and Image Separation:
We have analyzed the Tele-Graffiti feedback loop and derived the final steady state that the system converges to. We use this analysis to derive the optimal gain with which to set up the system to maximize the image quality; to minimize visual echoing, but to maximize how well the sketch from the other site is visible. We extended this analysis to Tele-Graffiti running with automatic gain control (AGC) and colour images. We have also derived an algorithm to separate the two final viewed images (which are a weighted combination of the two sketches at the two sites) into the two component sketches.