method for particle size over particle lifetime?

Is there a way to grow the particle size over the particle’s lifetime? I’d like to grow the trees on this image using the particle birth offset so that each tree grows as it appears.

I’m assuming you’re using particles and not hair.
Once your particles are set up so they just “pop in” at the moment when you want them to start growing, do the following:

  1. In your Particle System, under “Texture”, create a new texture. Name it “Growth” (or something)
  2. Go to the texture settings.
  3. Set the texture’s “Type” to “Blend”
  4. Under “Colors” check the “Ramp” box, and change the interpolation drop box from “Linear” to “Ease”
  5. Under “Mapping” change the Coordinates from “Generated” to “Strand / Particle” (this is the step a lot of frustrated people miss, by the way)
  6. Under “Influence” turn OFF “Time” and turn ON “Size”
  7. Tweak the settings for the texture’s Ramp to taste.

E.G. If your particle’s lifetime were 100 frames, and you wanted a 25 frame growth, then you’d have the ramp transition to full white in the first 1/4th of the available space. Basically, the more to the left the white side of the ramp is, the faster the particle will grow.

Thank you Benu… But I’m still missing something. I thought it might be a cycles only option, but that didn’t work either. It’s probably something amazingly basic. I’ve attached the blend file if that (392 KB)