grass terrain with multiscatter

[Crayox13]

So again, I'm doing test but I would like a theoretical opinion too.
Also, tests usually end up in 7 hour render estimate so...

Is it better to use MS to fill the area with like 5 million of these single grass objects (29 faces each-instanced of course), or to make a sort of grass bush (with 4396 faces) and 2 million copies of it. Math would suggest a single grass is better, but I'm not sure if vray/MAX/MS like 5 million copies of something.

Also, if Vlado can shed some light on "unloading geometry". When I do these tests I usually fill up memory and get unloading geometry. If I hit cancel then, vray will sometimes continue to unload geometry for as long as 10 minutes. Why does it take so much longer to unload something than to load it?

I set my dynamic memory limit to 5000MB, and have 8GB Ram.

[glorybound]

my understanding is, clumps are better. AS far as MS.... I can manually place 1000 proxies, or scatter it with MS, and the hand placed render a lot faster. Once I add a MS helper, everything slows down. The newest update helps, but it's still slow to render.

[windowlicker]

I have no experience with MS, but with Forest Pack, I've rendered millions of grass - both idividual and in clumps - and never had any problems.

However, for lawn grass (to medium high grass) I'm always using Vray Fur. It's incredibly easy to distribute, doesn't use a lot of memory and is reasonably fast to render. I use textures to control hight, denisty etc. which gives great variation to the grass, even over big surfaces. Just uvwmap your distribution object, and get going!

The image i've included was rendered with DOF at 3000px wide, taking 1h57m om a single machine. I'm sure it can be pushed further if you need to speed things up.

[Crayox13]

Thanks guys...I guess last time I tried to use vray fur for grass, couple of years ago, it had bugs or something because it also filled up my memory, so I stopped using it. I guess I'll try again.

[voltron7]

I've been using FPP and various grass clump models for awhile now. One thing I consitently notice is that the scattered clump grasses look better from a "laying in the grass' kind of viewpoint. Raise up the camera to 64" above grade and (at least mine) usually won't look quite as neat and trimmed like a mowed lawn does in reality (vs. wild field.) So I am going to try some VRay Fur again, because the majority of my paying jobs are in need of manicured kept lawns and not fields.) Thanks for the suggestion windowlicker.

[windowlicker]

Yeah, give it a shot. I'm using a 2sided material for my grass (even though it's not really recommended when using vray fur) and I found that to be fairly quick and reliable. I think most tutorials recommend using a refractive material, but I didn't get it to behave really the way I wanted to when I did my tests.

But workflow is the key for me. Most jobs call for grass that takes exactly 1 minute to setup, and with vray fur I get that simple workflow. Add all the grass covered areas into one object - Merge the readymade grass from file (I have a set of different types of grass to choose from) - Adjust the UVWmapping and texture size for your scene (bigger features when the grass is seen from a distance, smaller and more varied features when up close) - Assign the fur to the grass object - Render.
I've also used a "falloff" (usually a gradient mapped on another channel) from the camera to control the density of the grass, since you need less density the further away from camera the grass is. Saves memory and render time.

[voltron7]

@windowlicker
Thanks for the extra information on workflow. I am looking forward to trying it out again! I think the last time I tried to use Fur for grass was looong ago...

[raistlin]

Everything working with proxys take a bunch of ram, i'm working each days on really big scene and each have grass. The last i've done is set to 42 000m² and i've to optimise everything in an entire day of tests...
Mulstiscatter work approximatively like Forest Pack, i'm working with the two on several production, and if i'm using forest pack more than multiscatter now, it's just for the presets and facility to manage. Multiscatter is strong as forest to render billions of proxys as well.
You have 8 go of ram, and i can be pretty sure that's not enough...
For the first question, you can save your time anr ram usage in a tallest bush of grass, you can made a circle of 0.25m of radius with grass fields scatter on it, turn it to mesh and scatter again on your surface. Of course, bigger is your proxy, lesser you can scatter it along a path or road..., but you can done some limit to scatterise your "big grass" 50 cm far fot your road or path, and another with smallest grass proxy for the las 50 cm...
In all... Everything eat memory...
My 24 Go of ram is just valid to render my scenes...

[voltron7]

Yeah, give it a shot. I'm using a 2sided material for my grass (even though it's not really recommended when using vray fur) and I found that to be fairly quick and reliable. I think most tutorials recommend using a refractive material, but I didn't get it to behave really the way I wanted to when I did my tests.

But workflow is the key for me. Most jobs call for grass that takes exactly 1 minute to setup, and with vray fur I get that simple workflow. Add all the grass covered areas into one object - Merge the readymade grass from file (I have a set of different types of grass to choose from) - Adjust the UVWmapping and texture size for your scene (bigger features when the grass is seen from a distance, smaller and more varied features when up close) - Assign the fur to the grass object - Render.
I've also used a "falloff" (usually a gradient mapped on another channel) from the camera to control the density of the grass, since you need less density the further away from camera the grass is. Saves memory and render time.

Thanks again for the reminder about v-ray fur...I used it on last 3 projects and saved soooo much time! How do you go about using the "falloff?"

[chriserskine]

I'll also add that you shouldn't use lightcache with multiscatter. it ram usage goes through the roof with it.

[Morne]

I have no experience with MS, but with Forest Pack, I've rendered millions of grass - both idividual and in clumps - and never had any problems.

However, for lawn grass (to medium high grass) I'm always using Vray Fur. It's incredibly easy to distribute, doesn't use a lot of memory and is reasonably fast to render. I use textures to control hight, denisty etc. which gives great variation to the grass, even over big surfaces. Just uvwmap your distribution object, and get going!

The image i've included was rendered with DOF at 3000px wide, taking 1h57m om a single machine. I'm sure it can be pushed further if you need to speed things up.

[ATTACH=CONFIG]11929[/ATTACH]

how do you get the grass to taper like that with VRayFur?

[instinct]

how do you get the grass to taper like that with VRayFur?

Using the taper spinner i'd say

Regards,
Thorsten

[Morne]

Using the taper spinner i'd say

Regards,
Thorsten

hehehe ok. Geuss I havent used fur in a long time, or just always missed that option
but now I want to try it out

[samuel_bubat]

So again, I'm doing test but I would like a theoretical opinion too.
Also, tests usually end up in 7 hour render estimate so...

Is it better to use MS to fill the area with like 5 million of these single grass objects (29 faces each-instanced of course), or to make a sort of grass bush (with 4396 faces) and 2 million copies of it. Math would suggest a single grass is better, but I'm not sure if vray/MAX/MS like 5 million copies of something.

Also, if Vlado can shed some light on "unloading geometry". When I do these tests I usually fill up memory and get unloading geometry. If I hit cancel then, vray will sometimes continue to unload geometry for as long as 10 minutes. Why does it take so much longer to unload something than to load it?

I set my dynamic memory limit to 5000MB, and have 8GB Ram.

There is a little problem with Multiscatter or probably it´s more a Vray problem/way it is. If I recall it correctly it was fixed with Vray sp1 and is much better now
but it´s still there.
If you have many intersecting objects. Like really a lot of objects where multiple objects are intersecting you´ll get memory problems. A scene with
"just" 5 Million copies usually should render fine. So to quickly see if you´re running into this problem just scale the proxies with Multiscatter to something like 10%
and see if the memory problems are gone. If this is the case you´ll probably need decrease your count as it´s most likely way to much for the area anyway.
(That´s when I usually run in to this problem.. by placing more proxies than needed)

[simmsimaging]

I have no experience with MS, but with Forest Pack, I've rendered millions of grass - both idividual and in clumps - and never had any problems.

However, for lawn grass (to medium high grass) I'm always using Vray Fur. It's incredibly easy to distribute, doesn't use a lot of memory and is reasonably fast to render. I use textures to control hight, denisty etc. which gives great variation to the grass, even over big surfaces. Just uvwmap your distribution object, and get going!

The image i've included was rendered with DOF at 3000px wide, taking 1h57m om a single machine. I'm sure it can be pushed further if you need to speed things up.

[ATTACH=CONFIG]11929[/ATTACH]

Reviving an old one here, but how are you getting the render times under control? My typical setup just dies with Vrayfur or FPP scattered grass. Rough renders are fine but finals are glacial. What settings should I be watching out for mostly? I am currently rendering at 1/20 BF and LC, and with no GI.

p.s I have had good luck doing grass for small, high-detail areas, it is just killing me trying to get a large area (20mx20m or more) covered off. I'm rendering at 8K, which doesn't help either

/b