View Full Version : FFX and wind

06-18-2013, 06:33 AM
trying to give some faith to this hated tool again... in deadline :)
I managed to get grass haw i like, now client wants believable wind.
which are all the ways to do this ? beside texturing gravity or spay (or whatever), which is fakey, can i use FX wind or whatever ? If yes, i've to build guides before ?


06-18-2013, 07:35 AM
getting not so bad results animating just gravity now... anyway, is it normal FFX is not shown in VPR (Volume only not checked) ?

06-18-2013, 07:51 AM
Yes, it is. It is only rendered in vpr if the volume option is checked.

06-18-2013, 12:03 PM
in the end i gave up. Even tough i got not bad rendering in Volume only mode, rendering is incredibly slow... and gfrankyl i hoped i didnt need to build guides in modeler to have wind affecting fibers.
Not that animating instacnes locally is much simpler... you have to trick a lot to give instances individual movements. Large rooms for improvement...


06-18-2013, 08:04 PM
Paolo, you could add a turbulance procedural to your grass FFX bump channel and have a null as a reference object to blow 'wind' through it. It looks pretty good. You could even add a gradient on top to fade the displacement based on the grass's Fiber V channel.

06-19-2013, 11:38 AM
Hi Mike, thanks ! Yes i saw that, i tried and it was even quite nice... but i abandoned it because of uncanny rendertimes (really much much slower than instances).
Sadly, i confirm what i say: FFX is NOT a general purpose fiber solution, let's just call it HairFX.


06-19-2013, 12:04 PM
Even though I've had good success using FiberFX for hair and fur, IMO, it's not the best choice for generating grass over a large area--you'll hit a memory ceiling before you can get enough coverage for a large field. Instancer or the two other instancing tools will work much better for wide area coverage.

When I'm creating 'wind in grass' effects, I usually go for simple displacement tricks over dynamics--it's faster and much more controllable. Naturally, you'll want to do this with real geometry, not instances because I don't think you can apply world space displacement to instanced objects (I could be wrong though.) For distant windy grass, I render instances without wind effects and then I run animated 2D displacement through tracked masks in comp--this is a good cheap way to simulate wind blowing across wide grassy fields and valleys. It's very tweakable and you don't have to worry about it looking 'noisy'. I've used these techniques for many commercials and video game cinematics and the results were pretty convincing.

(Sasquatch worked well for distant grass too and it had a built in wind system. Of course, with Sas you'll have to deal with lighting and AA issues, depending on your output requirements and if you're compositing the results. I'm not sure how well it works for 11.5.)


06-19-2013, 01:15 PM
Instancing went good, big problem was animatin instances individually. SWe managed to get a good result with small grass clumps and some animated wavy gradients which acted on P angle of each clump, resulting in a nice "sea of grass" result. BTW it took about two day of experiments, because picking a way was not automatic at all. Man... this task should be a snap of fingers today. Both instancign animation and FFX need to make step ahead about this.


06-19-2013, 01:53 PM
That's cool! I recall trying something like that for a field of cg sunflowers using HD_Instance. I was able to animate a credible wave by displacing the source points which were generated using Random Cloner--but render quality of the sunflowers looked too noisy in the distance (there must have been millions.) I wound up rendering an oversized still-image as a matte painting for the entire sequence (it was huge because there was lots of camera motion in the shot,) and cut it up to get proper parallax effect. Then I did the 2D 'waves' gag described above in comp. Clients were very pleased with the results and hadn't even noticed I had completely replaced the live action footage with a carefully tracked 3D matte painting.