PVector array

Programming Questions

p3tr4s

in Programming Questions • 1 year ago

Hello,

I am trying to use PVector instead of x and y coordinates in Mover class. (There is an array of x and y coordinates.)

I believe, I made mistake by defining PVector array. Because I cannot access PVector coordinates to draw shapes.

Is the PVector array is written correctly or not? If not, how I have to write it?

What is more, how to get access to its v[i].x and v[i].y coordinates to draw shapes?

import processing.opengl.*;
import peasy.*;
import processing.dxf.*;
boolean dxfExport;
PeasyCam cam;
Mover[] movers = new Mover[5];
void setup() {
size(800, 800, P3D);
cam = new PeasyCam(this, 300, 300, 0, 1000);
cam.setMinimumDistance(1);
cam.setMaximumDistance(100000);
noStroke();
fill(160);
for (int i = 0; i < movers.length; i++) {
movers[i] = new Mover();
}
}
void draw() {
if (dxfExport) {
beginRaw(DXF, "myFirstGeometryOutput.dxf");
}
background(0);
ambientLight(95, 95, 95);
directionalLight(51, 102, 126, 0, 0, -1);
directionalLight(60, 60, 60, 1, 60, 0);
directionalLight(20, 20, 20, 0, -5, 0);
lightSpecular(0, 50, 0);
lightFalloff(1, 0, 0);
for (int i = 0; i < movers.length; i++) {
movers[i].update();
movers[i].display();
}
if(dxfExport) {
endRaw();
dxfExport = false;
}
}
void keyPressed() {
// use a key press so that it doesn't make a million files
switch (key) {
case 'x':
dxfExport = true;
println("DXF export complete!");
break;
case 's':
saveFrame("boxes.jpg");
println("screen grab made");
break;
}
}
//int[] xpos = new int[100];
//int[] ypos = new int[100];
PVector[] v = new PVector[100,100];
class Mover {
PVector location;
PVector velocity;
PVector acceleration;
float topspeed;
float a;
Mover() {
location = new PVector(random(width)*2, random(height)*2);
velocity = new PVector(0, 0);
topspeed = 5;
}
void update() {
}
void display() {
PVector mouse = new PVector(random(mouseX)*10, random(mouseY)*10);
PVector acceleration = PVector.sub(mouse, location);
acceleration.normalize();
acceleration.mult(0.2);
velocity.add(acceleration);
velocity.limit(topspeed);
location.add(velocity);
for (int i=0; i<v.length-1; i++) {
v[i].x = v[i+1].x;
v[i].y = v[i+1].y;
}
//for (int i=0; i<xpos.length-1; i++) {
//xpos[i] = xpos[i+1];
//ypos[i] = ypos[i+1];
//}
v[v.length-1] = location;
//xpos[xpos.length-1] = int(location.x);
// ypos[ypos.length-1] = int(location.y);
for (int i = 0; i<v.length; i++){
//for (int i=0; i<xpos.length; i++) {
stroke(255);
strokeWeight(1);
fill(255);
float c1 = 10;
float c2 = 10;
beginShape();
vertex(v[i].x+c1+48, v[i].y+c2, (i+1)*20);
vertex(v[i].x+c1, v[i].y+c2, (i+1)*20);
vertex(v[i].x+c1, v[i].y+c2, i*20);
vertex(v[i].x+c1+48, v[i].y+c2, i*20);
endShape(CLOSE);
}
}
}

Replies(13)

PhiLho

" I cannot access PVector coordinates to draw shapes."
What do you mean by that? Do you have an error message?
" how to get access to its v[i].x and v[i].y coordinates to draw shapes?"
I don't see where the problem / difficulty is.

Note 1: the declaration of acceleration as a field of the class isn't useful, as you hide it with the declaration of a local variable in the display() method.
Note 2: I cannot run your code, as I don't have the PeasyCam library... That's why I ask these questions.

p3tr4s

PVector array

1 year ago

Dear PhiLho,

Firstly, I am sorry for PeasyCam. I slashed out it, and now it works without it.

Secondly, the part of interest is Mover class.

The small story of the script I am trying to achive:

1. The script is basically a bunch of shapes(that consist of vertexes) that moves according to mouse position.

2. Then I included commands to get access to shapes that are drawn in previous frames.

3. But Second point was written in coordinates (xpos and ypos), but I wanted Vector coordinates.

xpos and ypos coordinates are slashed out and it works properly when I use them.

4. The main reason I want to use PVector instead of xpos and ypos:

I would like to do some vector math with PVector.

5. Problem: I want to draw shape between first frame and previous frames (between v[i] and v[i-1] vector cordinates, as a result I am writing v[i].x and v[i].y).

6. I added printscreen error picture.

import processing.opengl.*;
//import peasy.*;
//import processing.dxf.*;
boolean dxfExport;
//PeasyCam cam;
Mover[] movers = new Mover[5];
void setup() {
size(800, 800, P3D);
// cam = new PeasyCam(this, 300, 300, 0, 1000);
// cam.setMinimumDistance(1);
// cam.setMaximumDistance(100000);
noStroke();
fill(160);
for (int i = 0; i < movers.length; i++) {
movers[i] = new Mover();
}
}
void draw() {
if (dxfExport) {
beginRaw(DXF, "myFirstGeometryOutput.dxf");
}
background(0);
ambientLight(95, 95, 95);
directionalLight(51, 102, 126, 0, 0, -1);
directionalLight(60, 60, 60, 1, 60, 0);
directionalLight(20, 20, 20, 0, -5, 0);
lightSpecular(0, 50, 0);
lightFalloff(1, 0, 0);
for (int i = 0; i < movers.length; i++) {
movers[i].update();
movers[i].display();
}
if(dxfExport) {
endRaw();
dxfExport = false;
}
}
void keyPressed() {
// use a key press so that it doesn't make a million files
switch (key) {
case 'x':
dxfExport = true;
println("DXF export complete!");
break;
case 's':
saveFrame("boxes.jpg");
println("screen grab made");
break;
}
}
//int[] xpos = new int[100];
//int[] ypos = new int[100];
PVector[] v = new PVector[100];
class Mover {
PVector location;
PVector velocity;
PVector acceleration;
float topspeed;
float a;
Mover() {
location = new PVector(random(width)*2, random(height)*2);
velocity = new PVector(0, 0);
topspeed = 5;
}
void update() {
}
void display() {
PVector mouse = new PVector(random(mouseX)*10, random(mouseY)*10);
PVector acceleration = PVector.sub(mouse, location);
acceleration.normalize();
acceleration.mult(0.2);
velocity.add(acceleration);
velocity.limit(topspeed);
location.add(velocity);
for (int i=0; i<v.length-1; i++) {
v[i] = v[i+1];
}
//for (int i=0; i<xpos.length-1; i++) {
//xpos[i] = xpos[i+1];
//ypos[i] = ypos[i+1];
//}
v[v.length-1] = location;
//xpos[xpos.length-1] = int(location.x);
// ypos[ypos.length-1] = int(location.y);
for (int i = 0; i<v.length; i++){
//for (int i=0; i<xpos.length; i++) {
stroke(255);
strokeWeight(1);
fill(255);
float c1 = 10;
float c2 = 10;
beginShape();
vertex(v[i].x+c1+48, v[i].y+c2, (i+1)*20);
vertex(v[i].x+c1, v[i].y+c2, (i+1)*20);
vertex(v[i].x+c1, v[i].y+c2, i*20);
vertex(v[i].x+c1+48, v[i].y+c2, i*20);
endShape(CLOSE);
}
}
}

PhiLho

Re: PVector array

1 year ago

You know, such error is easy to copy & paste, it is easier to read as text than as image (and it is faster to load!).

benja

Re: PVector array

1 year ago

The null-pointer-exception is thrown, because you try to access the content of "v" before filling the array.
At the beginning all positions in the array ar "null", then you add one PVector to the array on every frame. It takes 100 frames until the array is full, so just check if "v[i]" is null, befor acessing it.

// when these values do not change, better define them once at the top of the sketch
    stroke(255);
    strokeWeight(1);
    fill(255);
    float c1 = 10;
    float c2 = 10;

    for (int i = 0; i<v.length; i++) {
      // only draw, if there is already a position stored
      if (v[i] != null) {
        beginShape();
        vertex(v[i].x+c1+48, v[i].y+c2, (i+1)*20);
        vertex(v[i].x+c1, v[i].y+c2, (i+1)*20);
        vertex(v[i].x+c1, v[i].y+c2, i*20);
        vertex(v[i].x+c1+48, v[i].y+c2, i*20);
        endShape(CLOSE);
      }
    }

p3tr4s

Re: PVector array

1 year ago

Jeeeej it works, thank you benja:)

One last question about vectors. I would be pleased you could help me, as it would be my final goal.

I would like to make shape - 4 vertex rectangle from two current frame vertexes and two previous frame vertexes.

The same mistakes occurs "NullPointerException" when I try:

for (int i = 0; i<v.length; i++) {
//The null-pointer-exception is thrown, because you try to access the content of "v" before filling the array.
//At the beginning all positions in the array ar "null", then you add one PVector to the array on every frame. It takes 100 frames until the array is full, so just check if "v[i]" is null, befor acessing it.
if (v[i] != null ) {
beginShape();
vertex(v[i].x+c1+48, v[i].y+c2, i*20);
vertex(v[i-1].x+c1, v[i-1].y+c2, i*20);
vertex(v[i-1].x+c1, v[i-1].y+c2, i*20);
vertex(v[i].x+c1+48, v[i].y+c2, i*20);
endShape(CLOSE);
}

benja

Re: PVector array

1 year ago

Same problem, you try to access an array-position that has the value "null". You have to check if v[i-1] is null too.
And you have to chenge the loop, to start with 1, otherwise you get an array-index-out-of-bounds.

for (int i = 1; i<v.length; i++) {
      if (v[i] != null && v[i-1] != null) {

            // drawing....

      }
}

p3tr4s

Re: PVector array

1 year ago

I finally understood how it works.... Thanks.

But strangely there is no rectangle, processing is drawing lines, instead of shapes?

Could you help me?

benja

Re: PVector array

1 year ago

The screenshot doesn't help very much, because the image covers a part of the code.
But there are two other mistakes in the code above:

1. The array should be a member of your class, otherwise, the 5 instances of Mover would all try to access the same array. so put it inside the mover class.

2. This is how you assign the values to the array:

v[v.length-1] = location;

This only stores a reference to the variable location. So in the end, you would have an array full of references to the same PVector. you have to create a new PVector like this:

v[v.length-1] = new PVector(location.x, location.y, location.z);

p3tr4s

Re: PVector array

1 year ago

Well, when I fixed these two mistakes, processing at least draws something, but it still do not connect v[i] and v[i-1].

Why does it happen?

What is more, how to deal with v[i+1]. I think, this means, that it is bigger than array length. How to write the same " if (v[i] != null ) {" but with v[i+1]?

Moreover, the code below is current one, with mistakes corrected you just told me to.

It is impossible to see the result as PeasyCam is slashed out, but the code works properly.

The main problem still exists as I cannot conect t v[i] and v[i-1] vertexes for perfect rectangle, ech... Please help me:)

import processing.opengl.*;
//import peasy.*;
import processing.dxf.*;
boolean dxfExport;
//PeasyCam cam;
Mover[] movers = new Mover[1];
void setup() {
size(800, 800, P3D);
// cam = new PeasyCam(this, 300, 300, 0, 1000);
// cam.setMinimumDistance(1);
// cam.setMaximumDistance(100000);
noStroke();
fill(160);
for (int i = 0; i < movers.length; i++) {
movers[i] = new Mover();
}
}
void draw() {
if (dxfExport) {
beginRaw(DXF, "myFirstGeometryOutput.dxf");
}
background(0);
ambientLight(95, 95, 95);
directionalLight(51, 102, 126, 0, 0, -1);
directionalLight(60, 60, 60, 1, 60, 0);
directionalLight(20, 20, 20, 0, -5, 0);
lightSpecular(0, 50, 0);
lightFalloff(1, 0, 0);
for (int i = 0; i < movers.length; i++) {
movers[i].update();
movers[i].display();
}
if(dxfExport) {
endRaw();
dxfExport = false;
}
}
void keyPressed() {
// use a key press so that it doesn't make a million files
switch (key) {
case 'x':
dxfExport = true;
println("DXF export complete!");
break;
case 's':
saveFrame("boxes.jpg");
println("screen grab made");
break;
}
}
class Mover {
PVector[] v = new PVector[100];
PVector location;
PVector velocity;
PVector acceleration;
float topspeed;
float a;
Mover() {
location = new PVector(random(width)*2, random(height)*2);
velocity = new PVector(0, 0);
topspeed = 5;
}
void update() {
}
void display() {
stroke(255);
strokeWeight(1);
fill(255);
float c1 = 10;
float c2 = 10;
PVector mouse = new PVector(random(mouseX)*10, random(mouseY)*10);
PVector acceleration = PVector.sub(mouse, location);
acceleration.normalize();
acceleration.mult(0.2);
velocity.add(acceleration);
velocity.limit(topspeed);
location.add(velocity);
for (int i=0; i<v.length-1; i++) {
v[i] = v[i+1];
}
v[v.length-1] = new PVector(location.x,location.y,location.z);
for (int i = 1; i<v.length; i++) {
if (v[i] != null && v[i-1] != null) {
beginShape();
vertex(v[i].x+c1+48, v[i].y+c2, i*40);
vertex(v[i].x+c1, v[i].y+c2, i*40);
vertex(v[i-1].x+c1, v[i-1].y+c2, i*40);
vertex(v[i-1].x+c1+48, v[i-1].y+c2, i*40);
endShape(CLOSE);
}
}
}
}

benja

Re: PVector array

1 year ago

I don't get what you want to do with all the calculation in your vertex-call. What are c1, c2, 48 for?
Anyways, there are rectangles, but they look like lines, because the difference between one position and the next are only a few pixels.
Tr to increase "topspeed", then you will see what i mean.

p3tr4s

Re: PVector array

1 year ago

OK, I want a rectangular shape that is drawn like this, or to simplify more:

I just want to draw a line between v1.x v.1.y and v2.x, v2.y.

then line v2.x v.2.y and v3.x, v3.y.

then line v3.x v.3.y and v4.x, v4.y.

then line v4.x v.4.y and v5.x, v5.y.

and till array ends.

Let say I write line command:

line(v[i].x+c1+48, v[i].y+c2, i*40,v[i-1].x+c1+48, v[i-1].y+c2, i*40);

and I get the result on the left and I expect to get:

benja

Re: PVector array

1 year ago

I think this is because you have "i*40" as z-coordinate. every rectangle will be drawn with at least 40 pixel distance to the one before.
Maybe try something like this instead:

        vertex(v[i].x, v[i].y, v[i].z);
        vertex(v[i-1].x, v[i-1].y, v[i].z);
        vertex(v[i-1].x+c1, v[i-1].y, v[i].z);
        vertex(v[i].x+c1, v[i].y, v[i].z);

p3tr4s

Re: PVector array

1 year ago

It works with (i-1), as I do not need vector in z axis:)

Ech now I am very very happy:) Thank you so much.

I think the major thing was when you told to me to use

Copy code

v[v.length-1] = new PVector(location.x, location.y, location.z);

and processing started drawing geometry. For now it is a bit difficult to know why this is not the same as v[v.length-1] = location; But I keep it my mind for following scripts.

After all, I thank you for your time:)

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