CAN WE BUILD A LARGE-SCALE, ART-DIRECTABLE FOREST WITHOUT CRAFTING EACH INDIVIDUAL TREE?
Glen Hamilton, Kansas
Weta Digital has created many digital jungles and forests comprised of unique trees and plants. We used to create them using our in-house tool Lumberjack, which procedurally grew individual trees in accordance with the principles of nature. Once the initial growth was done, artists could edit all aspects of the plant then hand-place it in the scene. The final look was effective, but the process was time-consuming.
Our work on War For The Planet Of The
Apes called for an immense, snow-covered forest of pine trees that gets annihilated by a powerful avalanche. We needed a faster way to build the forest without compromising our ability to art-direct each element, including the FX simulation for the avalanche.
We had to consider that trees don’t grow in isolation in the real world. The same species of tree will exhibit an infinite number of variances depending on their environmental circumstances. This rule of nature was the foundational principle behind the next version of our procedural trees system, Totara.
Totara allows us to grow trees in groups, forcing individual specimens to compete for resources just as they would in the real world. Older ones take over younger ones, sunlight and shade affect the density of branches and leaves, and access to water and nutrients affects growth. Totara accounts for all these factors and grows a forest across an input terrain geometry featuring environmental parameters defined by artists. The resulting forest features trees that are naturally varied in shape, size and distribution.
Developing Totara for this film paid off. As our hero Caesar narrowly escapes certain death in the final avalanche sequence, the forest setting shows remarkably lifelike distribution even in tight close-up shots. With Totara we can produce environments that look as detailed and natural as those with custom-sculpted models, in a fraction of the time.