Thanks Steve. I tried without the background draw thread on Mac and it works great. Also tested hiding the app. And my tree trunks or back, so it's all good. Full screen rendering is a bit better, but still a bit weird if you cancel it (and even if you don't). Because all the menus are disabled and without the save/close thingies it isn't obvious how to get back to the 3d view (pressing Escape several times does the trick). The other weird thing, in Shaded view everything looks B&W - trees aren't green like in Wireframe. - n8