New grass mesh, how to create? How "epic" did it?

[AlexCGart]

Hi,
I'd like to ask you guys about grass meshes. In many games I see that grass made like planes with opacity map. In UDK I see something different, in wireframe grass looks like lines, but in render mode it's same as planes with opacity map.
So here is the question, how Epic's did this grass? How can I create new grass mesh, what I need to use, any tools?
Just "plane-grass" drops fps more than grass from basic udk library. Where is the trick?

Thnx,
Alex

[apophis3d]

Pretty sure they did it with the speed tree plugin in UDK

[pulse0o0]

Their grass was just modeled as it has around 1500 tris on a single patch of grass so I am not sure why a plane opacity map version of the grass would reduce more FPS than the modeled out one?

[AlexCGart]

Problem is still not solved.

[pulse0o0]

I answered it for you they modeled it. As stated in my previous post.

[Spoondog]

Even though the modeled blades have more polys, they are faster because there is no overdraw (Farcry 2 did it that way aswell). They probably just modeled it in max.

[HavocInferno]

and how do you make them being affected by wind? epic's grass waves around in the wind

[AlexCGart]

Guys, take a look at udk grass without textures in editor - it's like 3 polygons for each "blade". They didn't modeled it with huge polycount. Something another here.. and I don't know what.

[Spoondog]

and how do you make them being affected by wind?

Look at the material for the grass - it will use World Offset Position and vertex colours to move the grass around.

[pulse0o0]

Well whether or not it's like "3 polygons for each blade" which it isn't I realize that is an exaggeration that doesn't change the fact that the small patch of grass is 150 tris and the large one is 1300, they are the same static mesh and it will be rendered as if your are seeing all of them even if you aren't. But as I see it they made many planes, use opacity and a World Position Offset.

[AlexCGart]

pulse0o0, thank you for trying to help. But, all what you said, it's a part of my question.
If epic's used just planes with opacity maps, why those planes in wireframe are lines? And why custom polygon with opacity map makes fps lower? What is the different between "epic's grass" and custom (standard for games this days) grass (polygons with opacity maps)?

[AlexCGart]

still need answer, help! ^ ^

[Xendance]

pulse0o0, thank you for trying to help. But, all what you said, it's a part of my question.
If epic's used just planes with opacity maps, why those planes in wireframe are lines? And why custom polygon with opacity map makes fps lower? What is the different between "epic's grass" and custom (standard for games this days) grass (polygons with opacity maps)?

Because they wanted better looking grass, that's why they didn't use opacity maps.

[seenooh]

Their grass do actually use opacity maps. I think the trick here is instead of using rectangular-shaped planes to represent a bunch of grass, they modelled each plane to match a leaf as much as possible. You can see that if you place the grass in the scene and switch to Lighting Only mode.

[redonix76]

AlexCGart, are you laying down your grasses by hand or using Deco Layer? If you're using the deco layer to put down a bunch of your grass, it's going to cause your FPS to spike. I've tested myself since I was also working on my own grass. Works fine as long as you don't use the Deco Layer.

[AlexCGart]

redonix76, I don't see reason why placed by hand can work better than grass with DecoLayer, may be you used too high density or some wrong settings. I can't imaging that I will put grass by hand on all terrain.
Anyway, it's not about how to put grass without lower FPS, it's about how to create grass in same way as epic's did, and this will be also give nice frame rate.
anyway, thnx.

[redonix76]

redonix76, I don't see reason why placed by hand can work better than grass with DecoLayer, may be you used too high density or some wrong settings. I can't imaging that I will put grass by hand on all terrain.
Anyway, it's not about how to put grass without lower FPS, it's about how to create grass in same way as epic's did, and this will be also give nice frame rate.
anyway, thnx.

Well the way you want to do it is no different from Epics. Same way as mine. I used 3 planes intersecting each other and a few supporting pieces with a Diffuse and Spec map. Works fine for me with no frame rate problem. I also created a patch of 800 triagles and it works fine placed by hand. So far I placed about 100 of them with no frame-rate issues. But if I used the Deco layer, even placing just 10 pieces will give me bad frame rate. That's why I'm doing it by hand.

Note: With me, even placing Epics own grass with the deco layer will give me a frame rate hit even a few like 10 patches...but I can place Epics grass by hand over and over again with no issues, I've tested this many times...not sure why that is.

Here is a screenshot of my grass:


Shot at 2011-01-20

[redonix76]

Ok so after a few tests, I figured out why placing grass with Deco layer is not good. It's because every grass patch will only cast dynamic shadows. It will only generate shadow maps if placed by hand.

If anyone wants to test this, place some grass with the deco layer and open up the Primitive Stats and take a look at the Shadow and Light map section, it's 0 kb. I then placed 1 patch of grass in by hand and it's popped up as 5 kb and the light and shadow maps magically appears in the new packages section.

Can someone from Epic confirm this please? Is there a way to force shadow maps in Deco Layer?

[AlexCGart]

After you will build light - all lags will be gone. To say that DecoLayer was made wrong and it's not good feature, sorry man.. it's a bit stupid- it's one of central features about level creations in UDK.
-----------------------------------------------------------
Anyway thnx for reply and research\ help.

[alvarofer0020]

so i added a long path of grass using deco layer

rebuilded lighting and i keep getting lagg

im using a pc with

a intel core 2 duo 2.6 GHZ

a nvidia geforce 9600 gt

and 4 gb of ram memory

[pulse0o0]

Well I think that is just attributed to your hardware and the grass is creating a lot of polygons on screen and your Processor and GC can't handle it though I am not sure this is the case as I upgraded to two 6970's OCed by 100mhz each and I have a 1090T Black Edition OCed to 4ghz and I still get lag on this option though when I take the time to place any mesh I don't get any lag so I am thinking that Redonix76 had the right idea.

[redonix76]

After you will build light - all lags will be gone. To say that DecoLayer was made wrong and it's not good feature, sorry man.. it's a bit stupid- it's one of central features about level creations in UDK.
-----------------------------------------------------------
Anyway thnx for reply and research\ help.

I never said it's not a great feature. I'm saying it wasn't made for placing grass to begin with that's what Foliage was for but they took that out. I systematically tested many options, took notes on memory usage, and what I got is "placing grasses with Deco Layer uses too much resources".

That's my conclusion whether you think it's stupid or not and it works out fine for me. I'm sure something new will replace Foliage and we'll have no problems later on.

Anyway, if you can get it to work fine with Deco Layer then that's great. My custom grass works fine for me my way. Anyone else with this issue please test it out and make your own conclusions.

[redonix76]

Well I think that is just attributed to your hardware and the grass is creating a lot of polygons on screen and your Processor and GC can't handle it though I am not sure this is the case as I upgraded to two 6970's OCed by 100mhz each and I have a 1090T Black Edition OCed to 4ghz and I still get lag on this option though when I take the time to place any mesh I don't get any lag so I am thinking that Redonix76 had the right idea.

I definitely agree that hardware plays a big roll in this. I've been in the game industry long enough to know a thing or two. I have a Nvidia Quadro 1700 GPU and it's great for Maya but it's not great for Games and OpenGL so I have to work around this as I go along.

PS: dynamic shadows is way more taxing then polygon count. At one point I had over 150K triangle for my grass patches and it works fine with shadow maps. With dynamic shadows it started affecting my frame rate about 15k. I'll follow up with you guys once I have all my grass in and have more stuff to show.

[redonix76]

so i added a long path of grass using deco layer

rebuilded lighting and i keep getting lagg

im using a pc with

a intel core 2 duo 2.6 GHZ

a nvidia geforce 9600 gt

and 4 gb of ram memory

The only way for me to get passed the lag with Deco Layer was turning off the Dynamic shadows. But it wont build a shadow map either though. Try that out and let me know how it goes.


Shot at 2011-01-20