Rendering samples of rt-weekend-rust.
Ray Tracing In One Weekend final scene with dragon (3840x2160, 1936 samples per pixel):
Cornell box with glass ball (2160x2160, 1936 samples per pixel):
Cornell box with metal dragon (2160x2160, 1936 samples per pixel):
smallpt scene from Kevin Beason (4096x3048, 1936 samples per pixel):