<layers>
<visual>

<param name="opacity" type="anim">
<duration>0.3</duration>
<style>linear</style>
<keyframe at="0.0">0.0</keyframe>
<keyframe at="0.5">0.25</keyframe>
<keyframe at="1.0">1.0</keyframe>
</param>

</visual>
</layers>