View Full Version : Controlling FiberFX density above 100% problem

10-24-2008, 11:50 AM
Hey guys, hope someone knows how to solve this issue I got...

Thing is, I'm trying to work on an outdoor scene with grass where the camera won't be too stationary.. So I thought to give a trick games use a go. To test it, I took a simple test scene (FiberFX shown here is not really what it can produce, it can be alot better :)). And I made the Fiber density (geometry created, pixel filter), dependent on the distance to a null object by putting a gradient in the T channel.

Result shown below:


Yay, all fine. Great. It goes from 100% in the middle (null is there) to 0 further away. A few issues though: the "Max Fiber density" # needs to be 100% too. If you put it on 0% and rely on the T channel (like in surface editor) it doesn't work. Furthermore, you can't do Fiber density in Node editor ( :|), lastly, you *can not* use Clump when T'ing the density. It gives crappy odd lines all over the place, as someone showed before here on the forum. (was a dirt track between grass). Annoying that that matters btw.

So 100% is clearly not enough, I want this alot higher. I could increase polycount, but since my scene will be slightly big, I rather not have M's of poly's just to keep FiberFX happy.

Solution: (I hoped)

Put Max Density to 900%, and the high point in the gradient to 900% too.


Hmm that went wrong... it looks like it is 900% all the way, except at the very edge where my gradient (coming from 900 to 0) finally drops below 100 untill the end.

I tried various layer blending modes in the T-channel and all kinds of odd things, but I can't get anything to work, that nicely blends from 900% down..

Anyone have a clue about this?

10-24-2008, 12:03 PM
Pff.. ok, doh..

See below:


I tried all kinds of blends.. and forgot "normal" at 100%.. :|
As you can see, it does exactly what I wanted. It is not completely clear to me why this "normal" works unlike it would work in for instance the surface editor (overwrite), but hey, it works :)

I'll leave the images here, perhaps the idea to make the density dependent on distance (to camera in the end) is of use to someone else.


10-24-2008, 12:21 PM
Before I run off to dinner, here a quick result if the null is linked to the camera and quickly tweaked:

Without distance dependence:


It took 2 min and 10 sec to render. (just for comparison)

With distance dependence:


Took 58 seconds!

I don't think the difference is that obvious and it opens options for my scene. I'll stop the one man spam thread now (couoldn't keep editing the first).

Cheers :)

10-24-2008, 08:06 PM
Been working with this grass for 2 days now, and have experienced roughly 50 crashes.. Getting a weee bit annoying.

Did anyone get results when trying to get a big area covered?

10-24-2008, 10:39 PM
Hey! That looks pretty good, and really nice render time on that last one there. I wish I could comment more on tests. I haven't done much with FFX in a little while. Just been modeling...

Someone get in here that has been using FFX and help this person!!

10-25-2008, 07:40 AM
thanks for that :)

I solved the crashes.. well solved... moving to a 64 bit OS did the trick of being able to avoid crashes (so far) and get to way higher fibre counts. My trick up here does still work btw, it gets increasingly better for huge scenes.

At first I didn't think memory was an issue. Since it only showed ~1.5 Gb in use overall when it crashes. But I guess it was.. Would have been sort of nice to get a notice of some sort that it is actually memory it needs, and not some odd program flaw (such as when using Viper or when opening particle emitter in the wrong sequence).

12-05-2008, 08:40 PM
This is the most promising example of grass I've seen with ffx

Right now i'm trying to make a very large field with grass and i'm really having trouble getting a large surface to look decent. Would you mind posting your scenes or your settings? Thanks

12-07-2008, 02:44 PM
I'm on the beta now and actually don't even have 9.5 retail installed atm anymore :|

To be honest, don't try to do the shot with FFX if you are not using a beta build. I ran into so many problems it's not funny (seriously, I was going mad). Beta builds helped.. they even fixed 2 bugs I sent in quite quickly. That in the end made it possible to get to an end result.

If you go for the beta ask again in that forumpart (if you don't get access rather quickly, do mail them), and I can see how to can help with a scene.

But beta's have their issues too ofcourse....

ps: I also went to 64 bit.. needed a decent bit of ram for a good FFX coverage of large surfaces..