Here is the structure synth code.

set maxobjects 500000
set background black
set raytracer::dof [0.26,0.02]
set raytracer::phong [0.6,0.6,0.3]
set raytracer::reflection 0.1
set raytracer::light [0,0,-29]

{ h 30 s 0.5 sat 0.6 b 0.1 a 0.8 } trunk
{ y 0.2 rx 70 h 30 s 0.5 sat 0.6 b 0.1 a 0.8 } trunk
{ y -0.2 rx -70 h 30 s 0.5 sat 0.6 b 0.1 a 0.8 } trunk

rule trunk weight 50 {
box
{ x 0.9 rz -2 s 0.99 b 1.15 h 5 } trunk
}

rule trunk weight 50 {
box
{ x 0.9 rz 2 s 0.99 h -5 } trunk
}

rule trunk weight 29 {
box
{ ry 15 rx -90 s 0.8 sat 0.9 } trunk
{ ry -15 rx 90 s 0.8 sat 0.9 } trunk

}