When creating very high resolution OpenGL rendered graphics of relatively complex models e.g. for presentation purposes or poster printing one faces the limitations of current OpenGL implementations. pOSRT is an offscreen rendering tool to create images of arbitrary size by means of MESA’s offscreen rendering capabilities and a stripe based multithreaded SMP-rendering approach to speed up the rendering process. Index Terms—Offscreen Rendering, multithreaded Rendering, Mesa, OpenGL, portable, wxWindows