This is probably problem which is faster to implement from scratch on your own rather for searching and trying to integrate some 3rd party libraries.
Implementing L-systems is fairly easy. You need to implement 2 parts.
The first part is string-rewriting system. It is simple. You just need to have a dictionary of rewrite rules (char key, string value) and then apply those rules for initial string i-times (where i is number of iterations).
Pseudo-code:
map<char, string> rewriteRules = {{'L', "L+R+"}, {'R',"-L+R"}};
string rewrite(string str) {
string result = "";
for each (char c in str) {
if (rewriteRules contains key c) {
result += rewriteRules[c];
}
else {
result += c; // identity
}
}
}
The second, harder part is interpretation of result string of symbols. The easiest way how to interpret turtle-like graphics in 3D is to use quaternions - it is simple to combine them.
Rewrite rules above are describing Dragon Curve and semantic meaning of symbols is:
- L, R: Draw line forward
- +: turn left 90 degrees
- -: turn right 90 degrees
Following code snippets are demonsttrating implementation of moving and rotating in 3D using quaternions. It is from my L-system interpreter written in C# (I hope you will forgive me :).
Quaternion rotationQuat = Quaternion.Indentity;
Vector3D position;
Vector3D forwardVector = new Vector3D(1, 0, 0);
Vector3D upVector = new Vector3D(0, 1, 0);
Vector3D rightVector = forwardVector.Cross(upVector);
public void Forward(double distance, bool draw) {
Vector3D moveVector = rotationQuat.Transform(forwardVector * distance);
Vector3D oldPosition = position;
position += moveVector;
if (draw) {
// draw cylinder/box from oldPosition to (new) position
}
}
public void Yaw(double angle) {
rotationQuat *= new Quaternion(upVector, angle);
}
public void Pitch(double angle) {
rotationQuat *= new Quaternion(rightVector, angle);
}
public void Roll(double angle) {
rotationQuat *= new Quaternion(forwardVector, angle);
}
So to interpret the string you just need to go through string and interpret each symbol. The simplest way is just switch:
for each (char c in string) {
switch(c) {
case 'L':
case 'R':
Forward(10, true);
break;
case '+':
Yaw(90);
break;
case '-':
Yaw(-90);
break;
default:
break; // do nothing
}
}
If you want to experiment with L-systems (even in 3D) there is nice web site http://malsys.cz where you can do so (Those C# snippets are from it :)
Good luck with L-systems!
