Willow Tree Process (Part 2)

Today, I figured I’d touch on my process for creating textures.

While many folks prefer to use a photograph for their texture, I’ve always worked from scratch, creating my own textures digitally, while referencing a large number of photographs for ideas and clues about growth habit.

With respect to trees, I usually start with a few variations on a base leaf, taking care to work out the base silhouette.

In the case of weeping willows, the leaves are narrow,oblong, and taper gradually. While the final  product will ultimately be much smaller and not show small details like serrated edges, I usually add them anyway, along with veins so that these elements can give hints of themselves later.

It’s usually a good idea to create a variety of different leaves, even if they are a slight modification of one base shape. This allows the final branch texture to have some variation to it, even if, at a distance, the differences are small.

Sometimes, the use of traditional media for texturing is helpful too. I have used my share of drawing tablets but (even considering the use of Cintiq tablets) none of them can truly replicate the intuitiveness of simply taking pen or pencil to paper and simply drawing.  Sometimes, it’s just easier to sketch out a base to work from, clean it up or paint over it, rather than drawing and erasing ad nauseum via tablet, and this is what I’ve done here.

This and some other branches were drawn with pencil, scanned, cleaned up and painted over.  Using this process, I was able to put together a sideways branch, which is now at a prime stage for the addition of leaves in Blender.

I usually start by unwrapping the UV of a plane to fill the whole area of a UV layout matching the proportions of my leaf texture. In the Node Editor, this object gets assigned a material with the leaf texture as a diffuse map. I additionally assign transparency to the material, using transparency from the texture to be the deciding factor in what gets rendered.

The plane gets cut up so that each piece of geometry gets a different leaf. I then also bring in the branch texture and put it on a vertical plane object (using a similar node setup as above) by adding it to my Diffuse Map node in the Node Editor.

Once this is in place, I divide the Blender windows such that I can view a preview in Render mode on one side as well as edit in either Texture or Wireframe mode on the other. This allows me to move leaf textures to match the branch texture relatively quickly, while still seeing the results (and how the transparent textures interact with each other) in real-time.

In this case, leaf geometry was laid out and duplicated with an Array modifier and also given a curve modifier, so that the geometry would conform to an extruded curve (to act as a stem). This allowed me to move and deform the long string of leaves in any way I wanted.

Special consideration is made to maintain variation and depth. Being able to use a 3D program to put together this texture means that I can take the time to create parts of the foliage which move forward or recede. Setting my texture workflow up this way also means it would be easy to replace the leaf texture later for other texture sets (fall colours, for example).

Once I have an arrangement I’m happy with, I add a solid emissive blue background, set up some appropriate lighting, position the camera and take a render (F12) of the camera view.

The result gets saved and opened in Photoshop. I select as much blue as possible, then delete it from the layer, leaving behind a transparent background. I then add a Hue/Saturation adjustment layer and de-saturate any remaining blue colour on the preceding layer.

Any additional cleanup should be done to the texture at this stage. I save a .PSD file as well as a .PNG at full size, then I repeat the placement process for branches along the full trunk. Once I have finalized placement, the file gets saved again as a .TGA, with an appropriate background & alpha channel and at a more SL-appropriate image size.

There can be a lot of experimentation at this stage and the solution, for trees, isn’t always a flat billboarded texture. As it stands, this tree still looks a little spare!

In my next article, I’ll show what additional geometry and texture work goes in to making the tree look believable from multiple angles.

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