the back story is I have been looking into ways to separate things into scene layers and rendering only what I need for each pass to be composite-ed later in order to save ram and render on the gpu. The scene has a few particle systems on the landscape that are rendering 15 trees or so each.
During my testing I found that disabling the “use hair” option in the render-layer properties made a big difference in the ram needed.
Then I decided to turn the hair back on and I could not get hair to render. The other particle systems that use hair but are rendering the tree objects worked fine. I tried in a new file and my linked character’s hair rendered fine.
I created a copy of my file to test things with then removed the linked groups that had the hair. saved the file, closed blender and then added the linked group again to test and still no hair.
I created a new empty scene and linked the character, added some lights and a camera and the hair rendered fine.
That told me that the original scene I was working in was the problem. So I kept working on it and after a couple hours of trouble shooting…
I discovered that if I added a cube with a particle system and at least 1 hair and rendered it, the hair would work again on my character. I just moved the cube to an unused layer after that and I was able to turn the hair rendering off and on several times and it worked as expected.
I saved my file closed blender and tested again and all is well.
I guess my conclusion is that the scene render settings became confused.
I am posting this in case it can help others. I am also curious if anyone else has seen this kind of behavior?
If anyone has a better fix for this that would be good to know as well.