Bark with Moss
For the final project in vsfx727, my team is recreating a live oak tree. The species resides throughtout Savannah, growing in dramatic sprawling forms. The reese also feature a wide variety of surface details, often with exposed flesh, knotted bark, vines, and exposed roots, making them particularly appealing subjects.
I began creating the tree shaders by updating my old bark shader. Using Voronoi influenced patterns, I gradually built up the bark surface in four layers. I began creating the displacement.
Layer 1: Large Cracks. Created with Voronoi distance formulas with noise. |
Layer 2: Noise within cracks added by taking the inverse of the large cracks. |
Layer 3: All over rippling added using turbulence functions. |
Layer 4: Moss created with a high frequency noise function. Because moss only grows on one side of a tree, the user is able to specify a moss vector. The dot product of the moss vector and the surface normal is taken to determine where the moss should grow. |
Layer 1: The ID of the voronoi cells is used to mix between different hues of surface color. |
Layer 2: To provide a weathered appeaance, dirt is added along cracks and in the center of the cells. |
Layer 3: Whever moss protrudes from the surface, the color is shifted to simulate moss covering the bark. |
This image shows the completed color scheme . |
Here is the completed shader, showing both displacement and texturing.
Then, I used Maya to apply the shader to a nurbs surface. Because the shader is based in S,T space, it follows the curvature of the surface with ease.
And here are the final renders, showing the trunk and a branch:
