or simply, add a "Syphon Server" to your comp, and connect an image, or set it to GL to send the whole openGL context (= what you're rendering) to MadMapper
sidenote: upcoming version of MadMapper (1.4) will have native QC rendering ability -- so you shouldn't need Syphon anymore in that case, apart for some live patching)
maybe http://www.madmapper.com/connecting-quartzcomposer-to-madmapper/
or simply, add a "Syphon Server" to your comp, and connect an image, or set it to GL to send the whole openGL context (= what you're rendering) to MadMapper
sidenote: upcoming version of MadMapper (1.4) will have native QC rendering ability -- so you shouldn't need Syphon anymore in that case, apart for some live patching)