• Document: Using the GPU to Create a Seamless Display from Multiple Projectors. Steve Nash, Nvidia Paul Green, Scalable Displays
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Using the GPU to Create a Seamless Display from Multiple Projectors Steve Nash, Nvidia Paul Green, Scalable Displays Agenda The Problem -- what do we mean by seamless? The way it’s been done up until now Our solution Scalable Display’s implementation The Problem Increases in pixel density and total pixels have not kept pace with increases in CPU and GPU power Different solutions for adding more pixels LCDs: obtrusive bezels in the way Nearly bezel-less The Problem (cont’d) Projectors: overlap the edges to hide the seam The Problem (cont’d) Projectors: optics (and screens) are never perfect The Problem (cont’d) Just creating the overlap makes a hot spot since the overlap region gets twice the light The Problem (cont’d) Projectors: how to project on domes and curved screens? Working with Multiple Projectors Current Nvidia SLI Mosaic product lets you specify overlap To be truly seamless, need to account for geometry and brightness differences between projectors The Solution Warp & Blend Warp = Geometry Corrections Blend = Intensity adjustments Can do one or the other, or both The way it’s been done up until now Hardware appliance for warp and intensity adjustment Expensive Extra performance delay tax on the display pipeline Additional complexity Software warp and intensity adjustment Applications need to be written to manage There has not been an easy way to implement this for any application, until now… NVIDIA’s Solution We can do this on the GPU! GPUs are fast, and are already have the pixel information Perform the transformation in the display pipeline before the pixels get scanned out By doing this on the GPU, we have more flexibility: high quality filtering, integration with SLI Mosaic, etc. NVIDIA’s Solution Works on Quadro 5000, 6000, and Quadro Plex 7000 Use it with G-sync to get synchronization between displays How’s it Done: Work Flow Take picture of calibration pattern Create warping mesh based on picture of calibration pattern relative to true image Typical Warping Mesh contains 1-10K vertices How’s it Done: NVAPI NVAPI is Nvidia’s programmatic interface to configure and control the GPUs. http://developer.nvidia.com/nvapi New interfaces are added in the 275+ NDA version to allow warping and intensity adjustment before the final scanout Currently works with single screen, multiple screen capability coming with R285 driver (mid September) How’s it Done: Warping 1. Initialize NVAPI 2. Get GPU Handle 3. Get Display ID 4. Define Warping Mesh 1. Use NvAPI_GPU_GetScanoutConfiguration() to get current desktop 2. Each vertex has: 1. x,y: 2D Vertex coordinates 2. u,v: 2D Texture coordinates 6 floats per vertex 3. r,q: perspective correction 5. Call NvAPI_GPU_SetScanoutWarping( NvU32 displayId, NV_SCANOUT_WARPING_DATA* scanoutWarpingData, int* piMaxNumVertices, int* pbSticky); How’s it done: Intensity Adjustment 1. Initialize NVAPI 2. Get GPU Handle 3. Get Display ID 4. Define Intensity Map: GL_RGB value for each pixel 5. Call NvAPI_GPU_SetScanoutIntensity( NvU32 displayId, NV_SCANOUT_INTENSITY_DATA* scanoutIntensityData, int *pbSticky); Scalable Display Technologies Scalable Display Technologies Leading provider of auto-calibration software for seamless multiple-projectors displays Founded in 2004, based on Ph.D. work of Rajeev Surati at MIT Over 100 Customers Command and Control Business Collaboration Visualization Simulation and Training Pro A/V Projector OEMs: 70,000+ licenses Core Auto-Calibration Technology (IP) ... Camera feedback to automatically warp and blend many projectors into one seamless display Patented by MIT and licensed exclusively to Scalable B€n€fit$ of NVIDIA W&B API • Scalable Display Manager (mil-sim, cmd&ctrl) • No longer need SDK integration • No need for warping box hardware ($$$) • Application Independence • Quadro support for Gen-lock Fewer requirements, barriers and restrictions means broader market and stronger growth B€n€fit$ of NVIDIA W&B API • Scalable Desktop (warped Win7 Desktop) • Full integration with Windows (login screen, ctr+alt+del) • Eliminates mouse pointer issues • Performance benefit • Expands potential outputs up to 24 100% integrated Windows solution Case Studies 100 MPixel Space Command and Control Navy Combat System Display 20 MPixel Touch Display Wall 48 MPixel F-16 Simulator Commercial Collaboration Systems Fortune 100 Collaboration room Oil and Gas viz room Classroom Info wall and whiteboard AFRL - 100 MPixel Space Command System 25 Computers with Quadro cards running 50 projectors

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