For example:

• ambient
• specular
• transparency

It might require either:

• changing the format (VRML most likely)
• perform some 3D geometry to infer the vertices of the faces of the cylinder (of radius R).

I currently think that the most accurate thing to do is to shift the axes to align to the center of the cylinder and draw the centered circle. Finally, these vertices are to be un-shifted to the original (global) axes.

A new definition syntax for L-Systems might be necessary.

Implement begin-fill and end-fill instructions which creates a face out of every vertex created in between.

See page 26 of http://algorithmicbotany.org/papers/abop/abop-ch1.pdf.

For example:

L -> [’’’∧∧{-f+f+f-|-f+f+f}]

can be used to draw (and fill) a simple leaf.

Hide output like:

; compiling file "/cl-lsystem/lsystem.lisp" (written 23 MAY 2019 08:58:10 PM):
; compiling (IN-PACKAGE :CL-LSYSTEM)
; compiling (DEFTYPE PARAMETRIZED-LETTER ...)
; compiling (DEFTYPE PARAMETRIZED-WORD ...)
; compiling (DEFCLASS RULE ...)
; compiling (DEFCLASS LSYSTEM ...)
; compiling (DEFGENERIC SET-RULE ...)
; compiling (DEFUN RULE-OF-PARAMETRIZED-LETTER ...)
; compiling (DEFUN PARAMETRIZED-LETTER->INSTRUCTION ...)
; compiling (DEFUN EXPAND-LETTER ...)
; compiling (DEFUN %ITER-LSYSTEM ...)
; compiling (DEFUN ITER-LSYSTEM ...)
; compiling (DEFPARAMETER *LSYSTEM* ...)
; compiling (DEFMACRO DEFINE-LSYSTEM ...)
; compiling (DEFMACRO DEFINE-RULE ...)
; compiling (DEFMACRO PARAMETRIC-WORD ...)
; compiling (DEFMACRO INSTRUCTION-CONSTRUCTOR ...)
; compiling (SET-DISPATCH-MACRO-CHARACTER #\# ...)
; compiling (SET-DISPATCH-MACRO-CHARACTER #\# ...)

; wrote /root/.cache/common-lisp/sbcl-1.4.13-linux-x64/cl-lsystem/lsystem-tmp5GEXGEG5.fasl
; compilation finished in 0:00:00.051

Problem

The parameter :initial-orientation which was initially meant to set the turtle's initial directions
introduces bugs in a 3D space when it comes to rotations (cf. turn).
It seems to do some axis shifting.

Proposed solution

Replace it by an :initial-direction parameter which sets the slot direction of turtle directly, instead of playing with rotations.

turn accepts a vector which must have only one non-zero coordinate which represents the axis (X, Y or Z) and how much to spin.
It would be better to have three distinct instructions:

• roll θ
• pitch θ
• yaw θ

Finding the index of a vertice in the list (cf. save/index-of) takes a really long time because there is a lot vertices in each branch!. Replacing that list by an AVL (with some v< comparator) may improve research time complexity (up to a logarithmic complexity).

See https://github.com/vy/avl-tree

The aim is to merge vertices that are close enough to smooth floating point imprecisions.

The list of vertices is read at most once at each insertion and position retrieval. Hence it makes evaluation and exportation each at least O(n^2).

(asdf:load-system :cl-lsystem)

triggers a lot of errors while

(asdf:load-system :cl-lsystem :force t)

does not.

Circle CI maybe?

The following code:

(process *plant-f* 7 (let ((env (make-instance 'png-environment :origin (v 0 -950))))
                                   (setf (direction (turtle env))
                                         (v 0.0 1.0))
                                   env) "refactor-plant-f")

generates the image:

which is wrong because the tree should grow following the Y axis instead of X.