Community documentation for implementing new commands

editor/docs/Implementing additional commands for undo-redo.md

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+How to implement additional commands for undo/redo functionality?
+===
+
+### Basics ###
+
+After evaluating different design patterns for undo/redo we decided to use the [command-pattern](http://en.wikipedia.org/wiki/Command_pattern) for implementing undo/redo functionality in the three.js-editor.
+
+This means that every action is encapsulated in a command-object which contains all the relevant information to restore the previous state.
+
+
+### Template for new commands ###
+
+```javascript
+	
+CmdXXX = function ( object ) {
+
+	Cmd.call( this );	// Call default constructor
+
+	this.type = 'CmdXXX';	// has to match the object-name!
+
+	// TODO: store all the relevant information needed to 
+	// restore the old and the new object-state
+
+};
+
+CmdAddObject.prototype = {
+
+	execute: function () {
+
+		// TODO: apply changes to 'object' to reach the new state 
+
+	},
+
+	undo: function () {
+
+		// TODO: restore 'object' to old state 
+
+	},
+
+	toJSON: function () {
+
+		var output = Cmd.prototype.toJSON.call( this );
+
+		// TODO: serialize relevant information so that 
+		// it can be restored in 'fromJSON'
+	
+		return output;
+
+	},
+
+	fromJSON: function ( json ) {
+
+		Cmd.prototype.fromJSON.call( this, json );
+		
+		// TODO: restore command from serialized information
+		
+	}
+
+};
+
+```