Also, how do you model those really cut surfaces on the rocks and other geometry. I’ve messed around with creating simple shapes like that, but they really rely on keeping the shapes planar, and as I edit the model and add detail I tend to really jack up the faces and then triangulation appears and then… poof it’s crap. I’ve considered trying to carve a rock with a boolean block, or using slice plane and capping over and over, but those processes sound very tedious.

Thanks

It seems like that would only work if your leaves are planes that have the same normal at each vertex. Which looks like the case for The Witness, I think. In that case that seems like a nice quick solution.

In my scenario leaf bundles are generally curved meshes with up to ~20 faces. I don’t think that method would work for me, since I don’t want bits and pieces of them vanishing when viewed on edge.

What I end up doing is clamping the mip level in the pixel shader. This prevents “lines” extended out into the transparent parts of the leaves when viewed on edge (I assume these are the ugly artifacts we’re talking about). I discuss it in the “Alpha-testing artifacts” section of a blog post here: http://mtnphil.wordpress.com/2011/10/25/vegetation-improvements/

there are some intersting papers on this topic, maybe some could help a bit.

http://graphics.uni-konstanz.de/publikationen/

sincerely

one thing I have noticed about the trees is there doesn’t seem to be any light coming through from behind. you could write a shader that when the normal is within a certain range (say backfacing) then you’d calculate a glow factor from the lights.

I know this is not a shader dev blog, but… yeah.

Excellent progress so far, I’m so excited to see this game progress, and it’s really inspired me in my own works.

Thanks very much for the insight

This shader, I’m assuming, would take the angle between the viewing vector, and the normal (by using a dot product), you would then have an “if angleBetween<someArbitraryAmount = discard triangle" type statement.

you could then add a fade to this etc to smooth out the effect.

That is one way of doing it, however I'm not sure if Ignacio used this or something more optimised.

I didn’t mention the normal maps I’m using because I didn’t want to get too detailed for this post…but I am using them. They’re kind of odd, a mixture of leaf direction and a hand painted map that both breaks up the leaves and rounds out the boughs.

We’re currently working on the LOD system, but once we have that going I could put up a quick post on it. Snake5, I should mention that while the tree is about 2800 polys, 1900 of that is the trunk. Only 900 are the leaves, so that might be one reason the trees are running pretty efficiently right now. I’m sure the trunk will LOD down pretty easily, too.

As for the shader, you might want to mention that to Ignacio next time he posts. I described what I was looking for, and he got it working, but I’m afraid I don’t really know the details.

http://www.youtube.com/watch?v=4IlgPpzXUZA

Look at those threes… not good. not good at all! my trees are like 50ps not 50k just 50 polygons. but do you think, …can i get a job?!

Seriously though, these trees are looking great! Are you also using a similar technique for the various hedgerows in the game or are these different?

Would you mind elaborate a little bit on this point ? I have similar shaders for my trees, but it turns out that the fadeout looks ugly when Alpha-To-Coverage is used ; especially on latest ATIs where they seem to have removed dithering for Alpha-To-Coverage (in OpenGL at least).

Do you use some ramp to modulate the polygon alpha according to its eye-space orientation ? Or is it something more involved ?

If you have got something for the LOD system working, is there any chance we can have a screen shot of the different poly models?

By the way they are looking awesome. You have inspired me to get on with more asset building :)

I do plan on making more types of trees, though I still want them to be volumetric. I’d rather err on the side of fewer types of trees than some trees that don’t fit with others. It’s a fairly small island, so I think I can get away with that.

One common trick to help smooth out the lighting is to edit the normals for the mesh. Here is an example using the Normal Thief script:

http://wiki.polycount.com/VertexNormal?action=AttachFile&do=get&target=Tree_Normals.gif

I have not used this technique though, so I don’t know much about it.

One interesting option suggested by the concept art is making the trees less naturalistic and more like topiary. A couple spheres with a dense texture of leaves, and then some tris outside of those, with a more sparce leaf texture could maybe work.

I think for our project we may end up going with aggressive LOD, and make dense “high” LODs. Transitions can be ugly, but I am not sure there is really any substitute with the current tech.

Stellar work.

You’ve been working out different modeling approaches to trees for what, 15 years now? SimCity, Spore and now these, which look the best of all.

I’m still using your “umbrella” technique, but with somewhat fancier lighting. I did a writeup here, if you’re curious;
http://oceanquigley.blogspot.com/2010/11/lighting-3d-trees.html

Yours look better though.

O.

I’m not entirely sure how you decide what is an acceptable compromise between visual quality and framerate when there is such a large range of target hardware capability.

You said they were too heavy at 12k polys, is that really too heavy? I appreciate modern games have that kind of budget for characters, but is the limit here imposed by the lighting system?

Either way, it looks like you’ve made some excellent progress towards optimizing the trees, though personally I think there’s something about the style of the 12k trees that just looks stunning.