Low Poly Foliage

EJtheArtist

Anyone have any tips or techniques for creating low poly foliage? Mainly: placing texture planes so objects look full in form and what your textures look like to do so? I really want to get better at making foliage, but its difficult to understand my low poly end goal.

Here's an example of what i'm working on. My plan is to improve the texture once I get the texture content I need and poly placement looking good. Right now they look extremely robotically placed, even at non 90 degree angles.

Reference images: https://trello.com/b/NXUwCPAl/wild-unkempt-bush

EJtheArtist

Getting warmer. Needs a normal map, maybe more flowers, and tightening up on the diffuse texture

Tobbo

Looking better. What modeling package are you using? Are you manually bending your vertex normals before export out of your 3D package?

http://wiki.polycount.com/wiki/Foliage

(It's toward the bottom of the page)

KrisLW

Definite improvement! Some things I try to keep in mind when making foliage:

When making textures, start small. Need a bush with flower clusters? Think smaller to just one element, like the flower cluster. Then the flower cluster is made up of individual flowers. Do the flowers have individual petals? If so, start off by making a flower petal texture and then working up.

Likewise, the same with the mesh - within reason. Just how "low" poly does it need to be? Sometimes larger shapes (like a cluster of flowers) needs to be broken down a bit (i.e. a single flower, or maybe a small handful) and then remade from the smaller element. Perhaps then the original low-poly made from the larger elements could be implemented as a LOD?

When creating your mesh, think round. Trunks/stems are always round, and thus, branches are going to spiral out around that. Not necessarily symmetrically, but "around" the plant none the less. A branch here, a branch there... hm, this space looks too empty, maybe I'll go back and add another there. Work organically as you see fit. Jump around. Plants don't always grow "in order."

Less foliage on the texture, more on the mesh. I've found that heavy clusters of leaves on a texture often end up getting mipmap'd into a solid block when working on bushes/trees. Compensate by adding more foliage planes to the mesh to make things thicker. I've found that I almost always end up needing to thin out my textures and thicken up my meshes.

Variation is everything! If I go outside, what I see as a square foot of "grass" might actually be something like 10+ different types of plants. In a natural environment, there will be tons of different types of plants growing together. In a highly manicured environment, like an estate garden etc, all of the "stray" plants will probably be weeded out - at which point focus your variation within each plant. Make 3 or 4 different leaves - slightly different colors, shapes, etc. Make multiple different flowers. Put the leaves in different patterns so you have several branch patterns, etc.

Also, take into account your material/shader settings in whatever rendering engine you are using. Light typically passes through leaves to some degree with a lot of scattering, usually resulting in a glowing appearance (rather than the backside being cast in shadow). Using a foliage/subsurface shader can make a very big difference, performance permitting, of course. No matter how nice you make your content, it's up to the engine to actually display it

EJtheArtist

Wow! Thanks for the great advice!

I'm using Unity 4 with marmoset shaders. I'm also using Maya to model/uv/mesh preview (which, btw, without the proper transparency settings in maya, transparency modeling can be a real pain!) Things that helped were: set viewport 2.0 to depth peeling and set the quality to 1, and also using flat lighting from the lighting tab.

Here's where i'm at atm. I painted the flowers and leaves in ps, and used crazy bump to extract a normal map, ao, and spec (which I overlayed the diffuse to pop out more details). I like how the texture came out (and please let me know if you see room for improvement), but I think my leaf card placement could use some work.



@Tobbo Is bending your normals for foliage (or anything else?) a standard thing to do? I've never heard of doing that before you mentioned it, but in the preview image, things certainly look better. How might I go about applying that practice here?

Eric Chadwick

This might help
http://wiki.polycount.com/wiki/VertexNormal#Maya

Cube Republic

I've made quite a few low poly plants myself. For inflorescent type plants you can add a single flower to your texture atlas. You then map this to a plane with an X cut across it so you can pull the edges out a bit. Add a few of these to create some fake volume on top of the globe of flowers.  

Ramseus

The card placement is looking pretty good to me in that shot, looks like the shrubby has some nice fullness.

Kind of an aside, but personally I've found the only way to get the depth I want out of my textures is to basically make all my textures in high poly and bake down, it's really the only reasonable way to get normal maps with leaves facing in different directions etc. It's definitely time consuming to do though.

EJtheArtist

@Ramseus  Yeah I wish i could spare the time to do a HP to LP bake. Maybe something similar to this? is there a particular way you go about it?

@Cube Republic That's a good idea, I'll probably do that!

thanks!@Eric Chadwick

i'll post an update this evening.

Eric Chadwick

We have a bunch of tutorials on the wiki about this workflow, worth a look.

KrisLW

EJtheArtist said:

 I like how the texture came out (and please let me know if you see room for improvement), but I think my leaf card placement could use some work.

I would personally suggest adjusting the diffuse map so that the dark/black outline around the leaves is gone. If it's applied subtly and naturally from a normal map, that's okay, but right now it doesn't look like shading as much as it's just a black outline that makes the leaves look artificial and flat.

Also, good luck with the normals - I think that will look great if you decide to try it.

Cube Republic

EJtheArtist said:

@Ramseus  Yeah I wish i could spare the time to do a HP to LP bake. Maybe something similar to this? is there a particular way you go about it?

I just build the plant using polygons. I use arrays and particles to get the job done faster. All the colour baking is done in blender using cycles render engine. I use xnormal or knald to bake normals, etc. I have a plane behind the arrangement to bake to, and a plane in-front to use as a cage. My method is basically this http://3dmotive.com/series/creating-foliage-for-udk.html  There's some of my stuff in my signature link.

EJtheArtist

So lol here's with the bent normals. It doesn't look too much different. What do you think? did i mess up somewhere? lol It certainly was fun modifying the vertex normals live in maya.... felt like controlling light with the force. *nerd



@Cube Republic  thanks for the link!

EJtheArtist

Is there a way I can paint meshes onto a mesh in maya? for example, if I wanted to paint leaf cards onto a sphere?

EJtheArtist

So it totally worked better on the next bush

EJtheArtist

Tobbo

Yeah it's definitely looking better.  

Eric Chadwick

Shading is better.

The leaf textures still have dark lines on the edges of the leaves. This makes it look stylized, which might be your intention. However it looks more like a Photoshop emboss filter than a deliberate painterly stylization. And the flowers don't seem to match that emboss style.

Steppenwolf

I would remove the dark edges around the leafs. You can try with Replace Color in PS. Ther's also a trick that you can use to create edge padding around the leafs. Duplicate the layer, apply gaussian blur on the lower layer, duplicate the blurred layer a couple times and finaly merge them.
Also i can recommend to add some subtle color variation to your leafs, goes a long way to avoid this uniform green look.

EJtheArtist

Thanks for all the help everyone! I'll see what I can do about the dark lines and color variation. Very good feedback and help! It really got me going on these, thanks!

EJtheArtist

is Normal Thief any different than the maya transfer attributes (for vertex normals) menu? 

Eric Chadwick

Yeah Normal Thief is basically the same but way slower, and limited to only affecting the normals. Transfer Attributes does much much more. There is a faster mod of that Maxscript, made by Slide London. http://wiki.polycount.com/wiki/VertexNormal#Slide_Normal_Thief_MAXScript

EJtheArtist

Here's a mini update with a beech tree I worked on today. I'm very happy with the results! Any ideas for improvement?



I'll update with textures/topo/workflow ideas later.

KrisLW

That tree is a night and day difference, great job! The foliage looks wonderful, my only critique would be that the bark is lacking; it's very flat and almost comes across as cell shaded since there is one side in light, and one side in dark, with no inbetween. (Although, that may be more about your rendering settings - some ambient occlusion would probably fix that)

I would also suggest investing a little time around the very base of the trunk, where the tree meets the ground. Trees never perfectly slice into the ground - the ground is always rough from the roots branching out, usually dirt/rocks with maybe a few sprigs of grass or something (since the tree sucks all of the nutrients up when it spouts, foliage around the base of a young tree is usually sparse) and some dirt on the tree trunk from rain splash-backs. (Or even moss, if it's a really soggy environment.)

EJtheArtist

@KrisLW  Thanks! I agree with you on both counts! 

Here's the texture. I first created the branches, just by painting simple strokes with a single color. Then added the leaves... painstakingly one at a time. I wish photoshop had a z-brush drag dot brush or something to quickly duplicate/transform/rotate. Know any better ways to place/transform leaves?

and here's the topo. I'm not yet a huge fan of placing branch cards. Mostly because I don't understand the most optimal way to place them. (Yet I enjoy UVing) Does anyone have any tips or workflows they use? What do you think about when you're making the card topology and/or placing the branch cards?

KrisLW

What you've got there as far as cards go looks pretty decent to me. You want to reduce "overdraw", since the computer has to actually render multiple times for transparency (for the cards themselves, then for what's behind them, then it has to decide how it's supposed to blend them based on what the transparency/opacity is.) Having an extra polygon or two on your cards to get a closer fitting edge is what you want, so the computer doesn't have to render vast areas of transparency for no reason.

As for placing them, it looks like you've done well. Ensuring the branches are actually "attached" and not floating, and you've got them all placed and rotated differently enough to visually justify their existence (if that makes sense - you don't want a duplicate looking like it's half an inch to the side of it's twin). Technically speaking, there might be a way to model the branches and place the cards via splines/curves - depending on the modelling software your using. If it'd be worth it, who knows - you'd just be diverting time off of manually making branches/cards and using that time to make the splines - and taking into account how easy or archaic it is to implement such a workflow in your software, it could go either way.

In regards to card placement, I think as long as you don't make floating branches, you can do pretty much whatever you want. Regardless of the type of tree you're making, natural growth seems to follow a very loose set of parameters that no matter how weird you think something is, there is probably a plant growing that way somewhere in the world.

For textures re: Photoshop, you could use a custom leaf brush with various dynamics so that you can just drag along a branch to place them. (The specifics of what settings to use would depend entirely on the brush head sample. For example, adjust the spacing, min/max sizing for size variation, add some hue/sat variation, and set to rotate according to the direction you're painting) I find that brushes leave a lot to be desired in regards to color, however, so you'd probably have to go back over the leaf base texture with a masked layer for adjusting the colors and adding variation on top.

Steppenwolf

Coming along nicely. The green shades on the leafs look much better.
As for branch cards, i tend to bulge them out in the center quite a bit (talking a bout the single card mesh) to give them volume so that from whatever angle you look at a tree you never see thin flat cards from the side killing the illusion.
Also you can make your life a little easier by grouping and copy pasting some cards instead of placing each one individualy. Made a tutorial about this a couple years ago:
http://polycount.com/discussion/86606

EJtheArtist

Good idea and tutorial @Steppenwolf, I'll try that next time I make a tree.

@KrisLW I also didn't think about "aving an extra polygon or two on your cards to get a closer fitting edge is what you want, so the computer doesn't have to render vast areas of transparency for no reason." I'll be sure to keep that in mind next time too.

As for the leaves, I still haven't found a more fun method to placing them. I did try to paint in leaves with a brush on a previous tree: turned out very... yuck. The color is greatly desired.

 Also the scattering and rotation. The leaves aren't scattered enough and too many are painted on in that one spot. I tried adjusting the brush, but summed that the time I was trying to tweak the brush settings, I could have been placing leaves lol. But if we could ever get this method to look good, it would be more fun. I ended up with a mixture of both methods.

The witness used that method on their trees and foliage. Orsi explains some of her process in the comments.