Frederic Bouvier:

Frederic Bouvier:

this patch introduce a new kind of animation and ssg branch.
I called them flash animation, because they help me to
enhance the look of the rotating beacon and possible future
lighthouse. It computes the cosine of the angle between an
arbitrary axis, transformed by the current modelview matrix,
and the view direction. No trig involved, just a dot/scalar
product.

The computed value can be modified by three parameters,
power, factor and offset, according to the formulae :

 value = factor * pow( cosine, power ) + offset.

It is clamped between a minimum and a maximum.
This value is then used as the scale factor of a matrix
transformation applied to the children of the SGFlash
branch.

The xml syntax, with default values, is :

<animation>
 <type>flash</type>
 <object-name>HaloObject</object-name>
 <center>
  <x-m>0</x-m>
  <y-m>0</y-m>
  <z-m>0</z-m>
 </center>
 <axis>
  <x>0</x>
  <y>0</y>
  <z>1</z>
 </axis>
 <power>1</power>
 <factor>1</factor>
 <offset>0</offset>
 <min>0</min>
 <max>1</max>
 <two-sides>false</two-sides>
</animation>