Per Pixel lit foliage and lighting

odium · Mar 2007

Just a quickie, for those of you in the know. How are you guys going about solving foliage in per pixel lit scenes with regards to harsh lighting? Simple planes with local maps are used for foliage but for the life of me I cant quite figure out a nice lighting method for them.

Is there any tips or links you guys could share? Thank you.

od

low odor · Mar 2007

This guy is getting some decent results in the D3 engine

Linkage

Xenobond · Mar 2007

I know that in max you can apply a modifier that'll let you manually edit the normals of the mesh.
I'll usually just grab all the normals and point them up a bit, so they all share more of the same direction with their normals.

Also depends on if your per-pixel scene can support normals edited in this way.

CrazyButcher · Mar 2007

depending on the size and kind, but for smaller grass bushes, I used the ground's normals.

http://crazybutcher.cottages.polycount.com/wip/worldlitparticles/20060930224107_00001.jpg

though the sample shows vertex-lit stuff.

what xenobound suggests, is similar. in my case it would have been the extreme that all normals point straight up, and the object aligns with the ground.

odium · Mar 2007

Unf... Damn, I need to read up on that Doom 3 foliage its just what I'm after. Thanks.

Joshua Stubbles · Mar 2007

I'm not sure what method they're using, but the foliage in the Armed Assault demo is lit very well. If you play it, you'd get a better idea. The grass itself doesn't seem to cast a shadow, but the projection shadows of the trees will cast over it.

hawken · Mar 2007

wow that is intensely real foliage. Only thing that makes it look CG are the humans!

John Warner · Mar 2007

thats totally incredible. shame about the characters...

Daz · Mar 2007

Yeah, a bit of a shame. That first shot is amazing though. I had to double take it looks that photographic. I don't remember the demo being that impressive. I'll have to take a closer look.

adam · Mar 2007

Yah wow.. I'm grabbing the demo tomorrow to check this out. Damn impressive.

Joshua Stubbles · Mar 2007

The pictures above are from an island not in the demo. Though the graphical fidelity is the same. You have to run everything maxed of course, for it to look THAT eyecandylicious. I'll post some pics from the demo here.

odium · Mar 2007

The problem with Armed Assault is that its a lightmap and soft cast shadow game, not full per pixel lit (ala Doom 3). So in other words, they can do all sorts of tricks with foliage to make it blend more into the enviroment. Light bounds in a lightmapped engine remember, so that instantly makes foliage look a lot better.

Joshua Stubbles · Mar 2007

Ah right, yes. It's certainly not per-pixel. It appears vertex-lit, but it's also self-shadowed with a projection texture

Here are 2 images I took from the demo:

I'll post a video later when I get the chance.

CrazyButcher · Mar 2007

is it really lightmapped ? they used to have dynamic day & night cycle with moving shadows (original opflash) I'd say they have one big shadowmap for "big objects" casted on small...
do the soldiers cast shadows on bigger bushes and such ? probably only small stuff + ground.

Joshua Stubbles · Mar 2007

It's real-time though, changing with time. Not a static lightmap. IIRC, the soldiers cast shadows on everything. But I could be wrong. I'll check again when I get home tonight.

Joshua Stubbles · Mar 2007

Here's a video I took tonight:

http://ivassago.com/temp/arma.avi

It might be a little hard to make out, but the tree's shadow casts on the soldier, and the soldier's shadow can also cast onto the tree itself. Pretty nifty stuff.
(video requires divx)

odium · Mar 2007

Thats just dynamic shadow mapping, its been around for a few years now. Trouble is, its still vertex lit. If you look closer you will see just how bad those shadows look.

Xenobond · Mar 2007

Those ArmA trees look a lot like Speedtrees, yo.

Eric Chadwick · Mar 2007

Speedtree uses sprite foliage, but Armed Assault is using crossing planes.

hawken · Mar 2007

still looks wonderful

I wonder who let those awful player models get through? when have you ever seen someone that pink except in cartoons?!

Eric Chadwick · Mar 2007

I think the lesson here is don't do per-pixel lighting on foliage. You might get the lighting looking OK if you tweak the vertex normals (my attempt here and here, not happy with it), but if there's self-shadowing the leaf-planes are not going to be good shadowcasters... too flat.

Completely-unlit vertex-colored leaves look great when done right.

Per Pixel lit foliage and lighting

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