Interactive Projection Game[CSEE 4840 Project Proposal - February 2008]Abdulhamid [email protected] [email protected] [email protected] [email protected]. INTRODUCTIONThe goal of this project is to design a system to create avirtual pool-like game using vision and projection technolo-gies.Game play is based on a projected image of a pool-table-likesurface, with a ball positioned on it. A player can t hen usea cue or cue- like object to ‘strike’ the ball. The ball is thenprojected in the direction it was struck and made to settleat a new final position from where the player can strike itonce again.The detection of the ‘strike’ is done using a camera whichcaptures the projected image with the cue stick over it. Theimage is then processed to determine the d irection and speedof the movement of the cue tip relative to the position of theball. The data gathered from this processing is then used tocompute the trajectory and distance of motion of the ball,if any, and reposition the ball appropriately. As the ballmoves and is repositioned, new images of the table and theball are redrawn and projected for the player to be able toadmire his stroke and plan his next one.The image capture and vision-based input is processed en-tirely in two dimensions. The implication of this choice isthat the angle of impact of the cue on the ball cannot bejudged or considered when processing the movement of theball.2. HIGH-LEVEL DESIGNThis section details a first-cut high-level data flow digramtogether with a list of components that are anticipated tobe incorporated in the design of the system.2.1 Parts List• Digital camera 1.3 Mega Pixel TRDB-DC2• DE2 Altera Development Kit• Standard Projector with VGA input2.2 Block DiagramFigure 1 shows a block level representation of the system.• Projector - We use an external projector which dis-plays images of the table with a ball placed on it. Theimage of the table is created with a high concentrationof saturated green so as to simplify the detection andprocessing of the black cue stick over this backgroundcolour. The projector receives data from the board viaVGA.• Camera - The TRDB-DC1 digital senses the imagedisplayed by the projector together with any shapeintroduced over the projected image.• Vision Sy stem - The vision system consists mainly ofthree elements (these are implemented in hardware):– Camera Interface - This component is in charge ofsetting the initial configuration of the camera ev-ery time the system is started u p. These settingsmay include such parameters as t he desired reso-lution, the number of frames that are desired to becaptured per second, and the gain for each colour.The interface is in the form of a serial interface tothe camera which is understood and implementedby a custom component on the FPGA.– Frame Grabber - This is a component that cap-tures 10-bit RGB values from the camera into aframe buffer by working at the appropriate pixelclock frequency. A double buffering scheme maybe useful to enable processing a frame while thenext frame is being captured and stored in mem-ory. The choice of the amount, if any, of memorythat will be employed t o hold one or more framesis based on the algorithm that is chosen for pars-ing the image to detect objects. At the moment,the exact algorithm, and consequently, the mem-ory requirement are not entirely clear. On thebasis of a preliminary algorithm that has been im-plemented and tested in a desktop environment,it is anticipated that one complete frame may berequired to be held in memory for processing. Thememory to be used is the SR AM memory. Thisdecision is based on t he superior speed on theSRAM.– Vision Algorithm.- The vision algorithm scans thecaptured raw image to detect the tip of the cueFigure 1: Block Diagramstick and return the ‘x’ and ‘y’ co-ordinates of thetip. Sample results from a simple implementationof an algorithm for this are included later in th isdocu ment.• Real Time Object Dynamics Simulator - The algo-rithm, implemented in software, calculates the positionand movement of any ball in the screen. This compu-tation is based on the ‘x’ and ‘y’ co-ordinates and the‘x’ and ‘y’ velocity vectors, which are determined fromimpact information received from hardware. Dampingfactors and collisions with borders are also incorpo-rated in the algorithm to determine t he placement ofthe ball.• Frame Generator - This module refreshes the framesto be emitted by the projector. This is implemented insoftware and involves configuring a display controllerwith information regarding the location of objects tobe drawn on t he projected image.• Display Driver - This last component in the chain gen-erates the signals for the VGA such as active video,blanking and synchronization. This is a physical layersignal generation block implemented in a VHDL mod-ule.2.3 Sample Results from Image Scanning Al-gorithmFigure 2 and Figure 3 show preliminary results from an algo-rithm that searches a bitmap for the presence of a cue stick.The image background is d esigned to be entirely green tosimplify object detection based on colours th at are observedin the captured bitmap.3. RISKS AND CHALLENGESWe foresee the following technical risks in implementing thisproject:1. Input frame processing - The precise algorithm and thecorresponding memory requirement in terms of framebuffers for the input is not yet clear. The speed of t hisprocessing is important as it could potentially affectsensitivity to the movement of the cue stick.Figure 2: Cue Stick Tracking ExampleFigure 3: Cue Stick Tracking Example - With cross-hair at cue tip2. Noise - The impact of noise in the incoming data andthe sensitivity of the camera is expected t o impact thealgorithm and its tuning.3. Calibration - The system is sensitive t o t he positionand orientation of the camera and the projector, andtherefore, changes in these elements can impact thecalculation of co-ordinates of various objects that aredrawn and detected.4. MILESTONES1. Milestone 1• Hardware implementation of the camera interface• Hardware implementation of the object detectionalgorithm through pixel scanning• Test-benches for the hardware implementation,and demonstration of image capture and pixelanalysis through a simple application that indi-cates t he co-ordinates of the object detected on aVGA monitor.2. Milestone 2• Thorough calibration of the system to
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