ArrayList reverse

Programming Questions

dredre1

in Programming Questions • 7 months ago

I can't figure out why my tree won't reverse. After it grows I want it to disappear in the opposite direction. Code is Daniel Shiffmans tree example and I used his Branch class.

ArrayList a;

float r= random (1,5);

boolean remove=false;

boolean finish=false;

void setup() {

size(600,600);

background(255);

smooth();

// Setup the arraylist and add one branch to it

a = new ArrayList();

Branch b= new Branch (new PVector (100, 300), new PVector (0.5f,-0.5f),300);

// Add to arraylist

a.add(b);

}

void draw() {

strokeWeight(.3f);

stroke(0);

for (int i = a.size()-1; i >= 0; i--) {

// Get the branch, update and draw it



Branch b = (Branch) a.get(i);

b.update();

b.render();

// If it's ready to split

if (b.timeToBranch()) {

a.remove(i); // Delete it

a.add(b.branch( 40f)); // Add one going right

a.add(b.branch(-40f)); // Add one going left

a.add(b.branch(-70f));

a.add(b.branch(50f));

// strokeWeight(100/a.size(1));



}}



if (a.size()>=200)remove =true;

if (a.size()>=1) {

if (remove) {

for(int i=a.size()-1; i>=0; i++) {

//

a.remove(i);







}

}}}

Replies(6)

Chrisir

Re: ArrayList reverse

7 months ago

maybe you need

background (0);

at beginning of draw ()

asimes

Re: ArrayList reverse

7 months ago

I can't run the code without the Branch class, can you include it?

dredre1

Re: ArrayList reverse

7 months ago

class Branch {

// Each has a location, velocity, and timer

// We could implement this same idea with different data

PVector start;

PVector end;

PVector vel;

float timer;

float timerstart;

float endX, endY;

float bLength;

float angRot;

//float r=random(100, 500);

boolean growing = true;

Branch(PVector l, PVector v, float n) {

start = l.get();

end = l.get();

vel = v.get();

timerstart = n;

timer = timerstart;

}

// Move location

void update() {

if (growing) {

end.add(vel); PVector start;

}

// Draw a dot at location

void render() {

stroke(0);

line(start.x,start.y,end.x,end.y);

}

boolean timeToBranch() {

timer--;

if (timer < 0 && growing) {

growing = false;

return true;

}

else {

return false;

}

// Create a new branch the current location, but chge direction by a given angle

Branch branch(float angle) {

// What is my current heading

float theta = vel.heading2D();

// What is my current speed

float mag = vel.mag();

// Turn me

theta += radians(angle);

// Look, polar coordinates to cartesian!!

PVector newvel = new PVector(mag*cos(theta),mag*sin(theta));

// new PVector = PVector (mag*cos (theta), mag *sin (theta));

// Return a new Branch

return new Branch(end,newvel,timerstart*0.6f);

}

asimes

Re: ArrayList reverse

7 months ago

This works, although you might notice that keeping 200 causes weird things to happen quickly. Basically certain branches will end up having some number of children and all the other ones are deleted.

It might be better to remove branches that are below some depth instead of some number of them. If the first branch had a depth of 1 and a branch with a depth of 4 is drawn, then maybe it would make sense to delete just the branch with depth 1. When you make branches at depth 5 remove branches at depth 2, etc.

ArrayList<Branch> a; // Best to cast as the kind of data the ArrayList holds
void setup() {
size(600, 600);
background(255);
strokeWeight(.3f);
smooth();
a = new ArrayList<Branch>();
Branch b = new Branch(new PVector(100, 500), new PVector(0.5f, -0.5f), 300);
a.add(b);
}
void draw() {
// Notice how this for loop goes backwards
for (int i = a.size()-1; i >= 0; i--) {
Branch b = a.get(i);
b.update();
b.render();
if (b.timeToBranch()) {
a.remove(i);
a.add(b.branch(-60));
a.add(b.branch(-30));
a.add(b.branch(30));
a.add(b.branch(60));
}
}
// A condition that counts depth would be better
if (a.size() > 200) {
int numToRemove = a.size()-200;
for (int i = numToRemove-1; i >= 0; i--) a.remove(i);
}
}
class Branch {
PVector start;
PVector end;
PVector vel;
float timer;
float timerstart;
boolean growing = true;
Branch(PVector l, PVector v, float n) {
start = l.get();
end = l.get();
vel = v.get();
timerstart = n;
timer = timerstart;
}
void update() {
if (growing) end.add(vel);
}
void render() {
line(start.x, start.y, end.x, end.y);
}
boolean timeToBranch() {
timer--;
if (timer < 0 && growing) {
growing = false;
return true;
}
else {
return false;
}
}
Branch branch(float angle) {
float theta = vel.heading2D();
float mag = vel.mag();
theta += radians(angle);
PVector newvel = new PVector(mag*cos(theta), mag*sin(theta));
return new Branch(end, newvel, timerstart*0.6f);
}
}

dredre1

Re: ArrayList reverse

7 months ago

Thanks for the help! I'll try to play around with it because for some reason it still seems to be growing on top of what I've grown instead of reversing.

asimes

Re: ArrayList reverse

7 months ago

Well, the background is never cleared. If you add background() to the beginning of draw() it might be more like what you want.

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