..
  This file was automatically converted from MediaWiki syntax.
  If some markup is wrong, looks weird or doesn't make sense, feel free
  to fix it.

  Please remove this comment once this file was manually checked
  and no "strange ReST" artifacts remain.

.. _automatic-texture-animation:

Automatic Texture Animation
===========================

It's possible to generate a model that automatically rotates through a
sequence of textures when it is in the scene graph, without having to run a
special task to handle this.

To do this, use the ``egg-texture-cards``
command-line utility. This program will accept a number of texture filenames
on the command line, and output an egg file that rotates through each texture
at the specified frame rate:

::
    
    egg-texture-cards -o flip.egg -fps 30 explosion*.jpg



This actually creates a model with a different polygon for each frame of the
texture animation. Each polygon is put in a separate node, and all the nodes
are made a child of a special node called a
``SequenceNode``.

The SequenceNode is a special node that only draws one of its children at a
time, and it rotates through the list of children at a particular frame rate.
You can parent the model under render and it will automatically start
animating through its textures. If you need it to start at a particular frame,
use something like this:



.. code-block:: python
    
    flip = loader.loadModel('flip.egg')
    flip.find('**/+SequenceNode').node().pose(startFrame)
    flip.reparentTo(render)



By default, all of the polygons created by
``egg-texture-cards`` will have the same
size. This means that all of your textures must be the same size as well.
While this is a simple configuration, it may not be ideal for certain effects.
For instance, to animate an explosion, which starts small and grows larger, it
would be better to use a small texture image on a small polygon when the image
is small, and have a larger image on a larger polygon when it grows larger.
You can achieve this effect, with the -p parameter; specifying -p scales each
frame's polygon in relation to the size of the corresponding texture.

::
    
    egg-texture-cards -o flip.egg -fps 30 -p 240,240 explosion*.jpg



There are several other parameters as well;
``use egg-texture-cards -h`` for a complete list.