This has been asked so many times before. I've got a snippet in the code archives, and a nice post with pictures here.
Rebounding of any angle
BlitzMax Forums/BlitzMax Programming/Rebounding of any angleThe Forum Archive is locked. These are the original blitzbasic.com forums, kept so their posts can still be read and searched. No new topics, replies or edits can be made here. To join the conversation, head over to the Blitz3D+ forums.