Question regarding amount and childrens of the hair particle system

Dear Blender Community,

I’m working on a architecture scene with much of grass in it. Im using a simple object for the particle system (12 faces, 4 blades of grass). To get a dense meadow, there are 3 of these in my scene, I need at least 600,000 copies of these grass tufts. What should I more increase, the actual amount of grass tufts or the children? I’ve learned that children will need less performance. I used a amount of 1000 and 600 render children.

My problem is that Eevee needs, with a RTX 2080 SUPER, 8 minutes to render. Are there options to optimize the scene?

At the moment I’m deactivating the meadows that aren’t visibile in the individual camera. That helps to get the render time down to 1.5 minutes.

Thanks in advance for advices

best regards


you can use two particle systems one with “high density” and one with “Low density”. and manage the weight groups for density on each with a dynamic weight paint brush object attached to your camera, painting dynamically on your floor canneva.

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Ok I understand it for 50 %. What is a weight paint brush object? I knew the function of weight painting. So I would paint the closer areas to the cameras with a weight map with high density particles and the grass in the distance with lower density.

Yes, you should use weight paint to make a gradient and ensure that the amount of particles are appropriate for their distance. You can also weight paint so that only areas that are in the camera’s view are placed which should save a bit more resources as unseen and unneeded particles aren’t rendered.

I would guess that skuax is meaning to use two particle systems that mix together in a gradient so that the low density (low poly?) version is for the furthest places, and the high density are for closer places. This would involve two gradients with weight paint, one that is strongest in the distance (for the low density particles) and decreases as it nears the camera, and one that is the opposite for closer details.

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Ok I’ll try that. Thanks for the additional Explanation :slight_smile:

It seems that weight groups done with dynamic doesn’t work with particles system. Better use dynamic texture paint instead.
Reading on blender bug mail that nobody fix it for the moment.