https://bugs.freedesktop.org/show_bug.cgi?id=30167
--- Comment #23 from Marek Olšák maraeo@gmail.com 2011-02-23 06:34:31 PST --- It could be. That FS input may contain random values because it's uninitialized, potentially leading to pixels being influenced by it, resulting in sort of random corruption. It depends on the shader and how much the input contributes to the final pixel color.