Paul Gifford wrote: > Re: adding the same map twice...each pass I make a new map (new as in > "valueMap = new ScalarMap(...)"). That's why I find the exception > perplexing. Unless you call display.clearMaps(), the Display keeps all the ScalarMaps around. You can call display.getMapVector() to get a list of the display's current list of Maps. You might want to grab that list and print it on each pass to help debug what's happening. As Doug said, I'd guess you already added the ScalarMap in a previous pass, which is why you're getting the error.