Hello, I want to change the opacity of particles used to represent engine flames which will be rendered out in hardware. Essentially I want the flames to die off/become more opaque towards the end like flames in reality. However its been a while since I've looked at particles so I'm wondering what settings I need to add/adjust in order to achieve this. I've tried adding in an opacity per object attribute, but I've already cached the particles. I can delete the cache but am also wondering is that going to screw up my animation? I don't think it should but then again...