Since 2002, Joshua has been the Lead Software Engineer (or "Head of Software Development") at Actuality Systems, a startup in Bedford, Massachusetts. The majority of his time at Actuality has been spent developing four generations of spatial 3-D displays and related application software. Joshua enjoyed a mixed role, dividing his effort between working as a hands-on developer, working with the customer to define real needs and working on fundamental technology advancements that drive the company forward.
Joshua led a team of seven software developers, being responsible for the software architecture, scope and schedule. He introduced a Scrum project management framework with a Test Driven Design policy. To support this development style, he designed a continuous integration system that provides a regression report for every submission to source control. The system uses boost's bjam tool to support both Microsoft and Linux builds. To shorten the team's edit-recompile cycles, he introduced the Incredibuild distributed build tool.
Joshua designed and helped implement the PerspectaRAD radiaiton treatment planning system (pictured on the right). The application made the unique advantages of the Actuality's display technology available to assist the complex task of optimizing external beam radiaition treatment plans. To perfect the feature-set, he worked with medical physicists and radiation oncologists from several different hospitals. He lead the project through prototype development and multi-institution preclinical study. The product is the recipient of the Society of Information Display's "Display Application of the Year" award.
Joshua also designed and helped to implement a medical volume image viewer (Perspecta Medical) and a seismic model viewer (GeoPerspecta).
Joshua determined opto-mechanical system design tolerances for 3-D volumetric displays. He created the calibration model along with a practical tool for measuring the calibration parameters. The tool simplified the process, making end-user recalibration feasible. The alignment matrices were factored and interpolated over radial sections of the display space.
Joshua also invented a system to measure and correct the performance and light transport functions of a multiview display. To quickly implement precise measurements of the display, he selected OpenCV for camera calibration and fiducial marker tracking. This system was designed to bring the actual lightfield of the display into agreement with the desired lightfield output. To accomplish this, Joshua implemented a constrained quadratic programming solver. The picture on the right shows a simulation of a naively rendered image, the desired image, and the appearance of the corrected image.
Joshua designed two real-time rendering engines capable of processing 100's of millions of voxels per second. The first was implemented with a custom DSP-based solution. The second was a distributed GPGPU rendering and image processing system. Actuality gained several patents for this work, covering novel rasterization techniques and rendering system architectures. Working on low-cost hardware, the system was stream "4-D" volumetric videos (such as a gated CT scan of a breathing torso). This summer, the 3-D display was featured in Scientific American.