FlightGear Newsletter February 2012: Difference between revisions

FlightGear Newsletter February 2012 (view source)

1,258 bytes added , 8 February 2012

381

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 === Did you know ===
+...that you can use expressions to create complex animations of objects in your 3d models or even drive them from multiple properties?
+Usually, an animation looks like this
+<syntaxhighlight lang="xml">
+ <animation>
+     <type>translate</type>
+     <property>foo/bar</property>
+     [..]more elements[..]
+ </animation>
+</syntaxhighlight>
+You can add a scaling factor or an offset to it, but that's basically all you can do that way.
+If you want to animate your object following a complex function, most people create complex Nasal scripts to compute the driving properties, probably not knowing that there is another way to achieve the goal: Expressions.
+Here is an example for a translate animation depending on two properties and the cosine function
+<syntaxhighlight lang="xml">
+ <animation>
+     <type>translate</type>
+     <expression>
+       <product>
+         <property>/my/factor-property</property>
+         <cos>
+           <deg2rad>
+             <property>/my/angular-property</property>
+           </deg2rad>
+         </cos>
+       </product>
+     </expression>
+     [..]more elements[..]
+ </animation>
+</syntaxhighlight>
+A rich set of predefined functions is available, including almost all those you have on your scientific pocket calculator.
 [[Category:FlightGear Newsletter|2012 02]]