I've been trying to get an answer or solve this for months. I'm using 4.1 and have a large computer with two large GPUs. It's new and has up-to-date hardware.
If I add an object to a hair particle system and then add wind the object flips it's rotation... along the center line of the object and not in the wind direction... when wind is activated usually at the 0 force point. That is crossing from negative force to positive force. The rotation flip does not follow the wind direction. It rotates along the original objects center as it is set up.
I set up as follows: Add a plane divided by 50 with slight deformation like a small hill. Set at center and apply all transforms.
Add a hair particle system with 25 for number. Add suzanne at center of grid with her base at the center and the origin set at the center. Apply all transforms.
I rotate my object (suzanne) on the y axis 90degrees so she lies on the grid with her center line along the x axis. Then make her the particle. This aligns the particles in the upright orientation (z). After this I do not need to check particle rotation or size. I do check global coordinates.
note: I've tried checking the object rotation box but it doesn't seem to make any difference once I set up suzanne for the particle system.
Add a wind force and animate it moving from 0 to -11 to +11 to 0. She rotates along the y axis as she should with the wind's direction but she flips front to back at 0 along her center axis.
note: I've played with adding a particle instance to suzzane and it's very heavy, very slow. I'm animating some large animations that will be displayed at HD on 4x7 foot monitors and this looks expensive to render. I hope it's not the only way to do this.
Can this be fixed so she always faces the same direction? I can't figure it out and it makes it impossible to do wind scenes this way.
