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Command Pattern in Realtime

Started by SlimTimmy Jun 10, 2004 at 6:07 AM 6 replies 2.2k views

Original Post

Jun 10, 2004 at 6:07 AM

Hello, I''m developping a terrain editor right now and want to use the command pattern to realise this Redo/Undo-Feature. But normally you use the command pattern for opening a document or something like this, that means just single events. But how should I use or modify the command pattern so it is possible to raise/lower a terrain in realtime?

SlimTimmy

Author

SlimTimmy

Jun 10, 2004 at 10:53 AM

*push*

fup

Jun 10, 2004 at 11:02 AM

The command "RaiseTerrain" is still a single event. If "RaiseTerrain" is the current command then that object will keep a record of how much the relevant terrain is raised. When the user releases the mouse button push the command onto the undo/redo stack.

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quorn

Jun 10, 2004 at 11:03 AM

At the start of the modification (e.g. mouse button down), store the state of the things that are about to be changed. At the end of the modification do the same again. Those are your two undo states. Make an undo/redo that has the knowledge (data and access to member functions) to be able to move between the two states.

SlimTimmy

Author

SlimTimmy

Jun 10, 2004 at 11:13 AM

Ok, thanks for replying.

Another question:
If the user presses the mouse button, I''ll create a command object of type RaiseTerrainCommand, and call the member function doAction(float elapsed). But I have to store this object somewhere and I have to call this method every frame till the mouse button is released. Is this right?