Unloading geometry and Multiscatter

[Crayox13]

Hi,
I'm new to MS, so I'm trying to create grass. I have few planes, not too big, just in front of a house, and 5 object that will make up the grass. It all went well until few days ago when everything slowed down. So I deleted all MS objects and started over. Now I have MS generate up to 4 million grass units. Basic leaves that are cylinders with 3 sides, and few plants with much less probability, so there are only few of those.

Anyway, the rendering is really slow. I would think that's normal but before that, the scene was pretty complex, with stone areas, as well as grass, all 3D objects. I keep getting "unloading geometry" which takes longer than it took to load it. On one hand, I feel this is normal, but still, maybe there's something wrong? I also tried tweaking the raycast parameters. To maybe reduce RAM usage (which would increase render times, I know) but I thought it would help not to load huge amounts of geometry. So I changed min leaf size to 4.0, and face/level coef to 2.0. Well, not much change. Any ideas? O, I have 8GB of RAM.

[jacksc02]

Sounds like you have some displacement causing you some memory issues.
Try unchecking displacement in your global switches and see if that helps.

[Crayox13]

I thought that as well as displacement usually gives "Unloading geometry" but I unchecked it in global switches and it still happens. Do you think it shouldn't happen? I mean 4 million grass leaves is not that much, right? That's max number, not sure how many are actually generated.

[vlado]

You can try increasing the "Dynamic memory limit" option in the V-Ray raycaster settings in the "System" tab of the Render Setup dialog.

Best regards,
Vlado

[Crayox13]

It's set to 4000MB...I'll try searching the scene a bit now, merging objects into a new one, etc. But I wanted to see you MS users, and other experts, if this is normal behaviour from vray, or am asking too fast renders for a complex scene. So this should go normal on my system? 2 Opterons 275, 8GB RAM.

[scheinbarreal]

Hello Crayox13,

I bought MultiScatter and iGrass six months ago but can't use it in production!
I can't render the iGrass fieldgrass samples because the rendering is really slow (Dell studio XPS i7850, 8GB ram).
Small and simple scenes work but regular scenes are running out of memory!
I would like to know how iCube made their showreal?!?

[Crayox13]

I still think I'm doing something wrong. I saw several renders here made with MS, and they looked really nice. Merging into a new scene didn't help, I'm trying reducing the amount of grass leaves now. Everything is so slow...so, it takes time to see what's wrong.

Still, Vlado, is it normal that "unloading geometry" takes about longer than it took to load the scene and render it? Also, when I click cancel in the middle of unloading geometry, it has to finish it first...but I guess that's normal.

Edit:
I didn't mention, but all of this happens during LC phase.

[PIXELBOX_SRO]

right, if you use the iGrass and merging the grassinto your scene, you have to SET the scattering density adequately to teh size of your plane.
Also, i dont recomment using LC...tends to be slow.
on my comp, the Multiscatter is very fast..much fater than Autograss

[Crayox13]

LC is for secondary, IR for primary. What is faster than that?

As I wrote, I don't use the iGrass, but made my own. It was composed of several different leaves, now I reduced them to speed things up. Now it's 2 different leaves (just differently bent), few small bushes with really small probability, and a bush made of grass leaves arranged in circular fashion. It's a bit faster now, I used to have two more grass leaves but I also reduced the number from 4 million to two. Will post the results. What kind of grass leaves do you guys use?

[PIXELBOX_SRO]

try IR/BF
look in my post in GENERAL section

[Crayox13]

Ok, after many trial and errors, Vlado, is it normal that if I spread about 2 million objects that have 30 faces each (making a grass object) for vray to use about 6GB of RAM and keep unloading geometry? All objects are scatter using MS, so they are instances. Not sure how to get the exact number of objects with MS.

[retardus]

Hello Crayox13,
Have you checked the material assigned to the iGrasses?
I don't own iGrass, but I have some autumn iTrees and found that the iCube folks created some pretty complex multi-materials w/ all kinds of glossy reflections. They render MUCH slower than trees I created myself with a much higher polycount. I have yet to render a test w/out reflections and am not sure know if this is the case w/ iGrass. Be nice to know as I am currently looking for grass myself.
Sincerely,
Retardus

[Crayox13]

Hey,
I don't use iGrass but made my own, so not really sure, put PIXEL does.

[PIXELBOX_SRO]

yo, its not the material....those r fine....might be worth asking more experienced ppl like BBB3, who uses multiscatter quite a lot in his exterior scenes.
have you tried converting your objects to proxies and then scatter? or the other way round?
might it be that your objects have issues in the 1ast place?
how do they stand when compared to the igrass objects? i mean polycount, object type (poly, mesh, patch) etc....

[jacksc02]

I have had issues with Multiscatter and unloading geometry and the best thing to do is to raise the dynamic memory limit and not use Light Cache.
Reducing the bucket size can also help.