How to animate a material during the life of individual particles?

Hi,
How to animate a material during the life of individual particles ?
I’m trying to build a scene with the rain falling on a hot pavement.
I’d want to show each drop making a stain, and each stain dissolving.
I have used billboard particles for the stains, with a UV Blend Halo or Sphere texture for the shape of the stains, and alpha.
I have set up an Alpha Ipo for the material, starting to decrease when the drops (dead particles on the ground plane set to collision) are sticked on the ground.
The problem is that the material alpha is decreasing for all particles, even those that are not yet dead and still falling.
I have choosen “Time” for the billboard texture animation ,and tried with Global and also Absolute in the Extras panel, without any succes.
Is it possible to set up the Alpha (or an other parameter of the material) in order that it changes along the life duration of each individual particle instead of alongthe global time of emission of all the particles ?
Thanks in advance !
Philippe.

Alpha values work differently with billboards than with halos and I think there is no other way than to animate the billboard’s alpha texture by splitting the texture / moving the UVs. For this kind of setup, I haven’t found any other method than to create two tiled images and would be very glad if someone shows easier way to do it.

Texture setup: Other one has the color info (stain in your case) split as many times as the other texture that has the alpha info (fade). Actually, since it is compulsory to duplicate the color info too, you might just as well animate it afterwards.

Here is a tutorial for animating billboard’s textures, if you don’t know the method yet. There is also a link to a Gimp script by which you can create the tiled image more easily: http://vimeo.com/1412840.

Thank you very much for this very interesting tutorial !
As I will need a big texture grid, it is a bit heavy to setup my scene using tile textures, but it is good to know this method.