Planting Digital Trees

Planting Digital Trees
Posted by on November 15, 2012
Posted in: software, tips and tricks

Trimble Sketchup is an ideal platform for rapidly creating rectlinear 3d models. With practice, Sketchup modelers can construct extremely complex geometric forms. However, Sketchup’s straightforward, stripped down interface offers few “out of the box” tools for creating organic shapes, such as trees and shrubbery.

Although it is possible to digitally model every trunk, branch, and leaf, such a strategy is resource intensive. It takes a lot of operator time and computer power. Over the years, we’ve learned about some better options to represent trees and shrubs to a digital model.

2D – The simplest method is to avoid modeling altogether. Instead, we use a photograph or hand drawn image of the desired tree, on a transparent background. The image is imported to Sketchup as a flat, rectangular plane, and converted to a “face me” component, with its axis of rotation set in the middle of the trunk. Now the tree image will always appear to be facing the camera, no matter what perspective is chosen for the scene. This strategy works well for simple diagrams, viewed from the ground, or a low altitude. When lighting is required, we can trace the outline of the tree to create an invisible “shadow mask”. To avoid both carpal tunnel and stress headaches, a Wacom stylus and pad help to produce accurate, free handed contour lines in seconds, compared to a good five minutes and multiple undos with a mouse. The result is a good approximation of the shadow that would be cast by an actual 3d object.

 

  • Photograph of a Big Leaf Maple imported into Sketchup. Despite the transparent background, Sketchup only sees a rectangle.
  • The same Big Leaf Maple, set to face the camera and shadow disabled. Instead, a hidden plane has been trimmed to approximate the trees outline and cast a shadow.
  • An overhead shot reveals the limitation of 2D photograph trees.

2.5D – A second method retains most of the speed and low computing requirements of the 2D approach but offers more realistic shadows and better aerial views. The graphic effect blurs the line between a flat image and 3D object. We often use a set of components developed by Tom Sailor, a SketchUp and PhotoShop wizard based in Manhattan, KS. His trees and shrubs have an array of semi-transparent foliage images placed onto a simple 3d trunk and branch structure. The 2d images are placed at a 45 degree angle so they still look realistic when viewed from above. The components include both horizontal and vertical shadow masks. These trees provide good results as entourage in photo-realistic renderings, and it’s possible to add dozens of them to a SketchUp model without slowing down performance too much.

 

  • A 2.5D tree, with multiple images arranged along a 3D trunk. A hidden, shadow-casting shape is also used.
  • A 2.5D Tree without camera facing, seen from the side.
  • An overhead shot demonstrates the 2.5D advantage.

3D – In SketchUp, this is usually an option of last resort, because of the computing resources required to store and draw all the details (down to each individual leaf) in 3d. This sort of tree can balloon file size and redraw time, especially if the model calls for many copies. However, a well designed 3d tree based entirely on polygonal construction, does provide the most flexibility for viewing angles and best realism & shadow accuracy in close up views.

 

  • A true 3D Tree. Each branch and leaf is modeled in space, and casts a shadow.
  • Though demanding more resources, 3D Trees maintain greater detail than any other technique.

Of course, these are just a few examples of the solutions we have employed to depict trees and shrubs in landscaped models. The SketchUp community is very creative in coming up with new ways to extend the usefulness of this simple 3d modeling platform, and we are are always eager to find the next great idea. So if you have any suggestions for how to incorporate trees that were not covered here, please drop us a line!

About Jeff

Jeff Harris was an intern at Fat Pencil Studio in 2012.