Trees

 I remember that when I made my first abortive attempt at Caravanserai a couple years ago, one of the first things I tried modeling was an olive tree. It didn't turn out too well, but I barely knew my way around Blender yet. I worked on that tree for a good long while, too.

Today, I modeled a mastic tree, the source of mastic gum and mastic resin, which are used throughout the Middle East as flavoring agents, often for sweets, such as Turkish delight (although my favorite flavor of loukoumi is rose).

The Number 1 secret to a good model is to work with a good reference. Mastic trees have this characteristic curving, twirling habit, so I wanted a reference that really exemplified that. This is the one I ended up using:

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Once you have your reference, save it to your computer (I keep a references folder for each .blend file I have for organization). Then, in Blender, go to Add > Images > Reference and navigate to where you've saved the image.

The second key to a good model is working at the appropriate scale. imported the Morrowind Tri_Shadow mesh so I could tell how big to make the model. This looks like about how big I want it to be.

For trees, I like to start with a cylinder. Another trick that I use is that I make sure all my models have geometry down to -1 meter. That way (as long as the origin is at 0,0,0) you don't have to worry about placing the model on level ground when it comes into Unreal.

Take the top of the cylinder and, in X-Ray mode, scale it be the correct width of the tree based on your reference image. Then just extrude it to another segment, scale it, rotate, etc. When you get to a point where the trunk branches, merge the vertices on the top of the cylinder.

Now, take half of the faces to match up with the way one branch goes and make them spherical. To do this you can go to Mesh > Transform > To Sphere, or you can hit Alt+Shift+S. When you're done, you'll have this funky shape (or something like it):

Grab all of the faces on one of the "spheres," rotate it and move it around a little bit to match up with the branch in the background, then extrude it. Follow the branch in the reference image until you reach the end. If you lose the branch in the foliage, don't worry about it too much. You can keep going using your intuition or just end it there.

When you get to the end of this process, you're probably going to find that your tree doesn't have a lot of dimension, because you've been tracing a two-dimensional image. 

One relatively easy (and fun!) way to fix this is to add an armature. Once you've done that, you can go into pose mode and move the branches around to give your model more of an arboreal shape. You can even duplicate your mesh at this stage and make multiple poses for more variety in your trees.

For the foliage, I like to start with icospheres, since they don't get much play otherwise. I also like to make them as separate objects, that way we can set the foliage to have no collision if we want. Just move the vertices around until you've got a shape approximating the foliage. I like to do this with a little proportional editing turned on, using the round shape. Sometimes I do a couple of passes of randomizing the vertices and then smoothing them back out to make the shape a little more chaotic. Just make sure that your foliage object covers up the tips of the branches.

If you are going to have no collision on your foliage object, select the whole thing, duplicate it, split it, flip the normals and scale it in a little bit. This way, you'll have a copy of the shape on the inside with normals that face inside, so if the player ever goes inside of the foliage, they'll still see it.

The last important thing to do in order to get a good result is to have fun with it. Try things out, add a modifier, turn on proportional editing. And, if you're doing low poly like me, don't sweat the finer details too much.