I want to populate trees along a road with Particles using weight painting to control the density. My problem is that the particle system needs to know the final particles count - logically, I proceed from start to finish so with every newly painted areas, the tree density will more and more decrease as this number spreads to bigger area. This means I have to adjust and estimate the count every while, which is frustrating. So is there any option how to tell the particle system to produce maximum (based on a weight paint) of 5 instances on area of i.e. 10x10 meters so the number of instances / particles will grow progressively as I paint? enter image description here enter image description here enter image description here

  • $\begingroup$ If you use a Hair Particle System you can influence the Length instead of Density $\endgroup$
    – HenrikD
    Jan 21, 2019 at 8:23
  • $\begingroup$ @HenrikD I tested this now and it doesn't look like this changes particles count. $\endgroup$ Jan 21, 2019 at 11:35
  • $\begingroup$ No but you dont need to adjust it. You just need to have all the particles you dont want to be invisible (scaled down to 0) $\endgroup$
    – HenrikD
    Jan 21, 2019 at 11:37
  • $\begingroup$ @HenrikD But this way milions of trees / particles will be hidden and only those in weight painted areas will be shown...? $\endgroup$ Jan 21, 2019 at 11:42
  • $\begingroup$ yes! I dont know how much it affects the performance, you have to test it. $\endgroup$
    – HenrikD
    Jan 21, 2019 at 11:43

1 Answer 1


As I haven't found any solution so far and this fixed-count workflow limits my daily work a lot, I have refreshed my "so-so programming skills" and I ended up with creating a Blender (2.79) addon which does this job for me.

With the addon, you set the Density parameter and the Emmission Number is adjusted accordingly:

enter image description here

I have placed the addon to Github and would be very happy is someone can test it and report any bugs. https://github.com/jendabek/blender-particles-density

  • $\begingroup$ Ah, a great addon! Can surely use it if not recommend it to my friends! It has a similar function as the density in Graswald $\endgroup$ Apr 26, 2019 at 18:10
  • $\begingroup$ Thanks, first I would like anyone to test it properly as I am not very skilled Python programmer and even it works for me flawlessly, there can be some bugs when i.e. using some different workflows... $\endgroup$ Apr 26, 2019 at 18:23
  • $\begingroup$ OK, can I rewrite it to work with 2.8 or do you want to do that yourself? Asking since I want to get better at coding too $\endgroup$ Apr 26, 2019 at 20:32
  • $\begingroup$ @DrachenSeele Of course, just create a branch or something like that :) $\endgroup$ Apr 27, 2019 at 8:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.