How to use a for loop and the array function to create a tail for a bouncing ball

Programming Questions

el_brendo

How to use a for loop and the array function to create a tail for a bouncing ball

in Programming Questions • 2 years ago

Large subject title huh? It pretty much captures my current predicament.

This is my current code, with what is needed following:

int balls = 100;

float[] xPos = new float[balls];

float[] yPos = new float[balls];

float xSpeed, ySpeed, posMorpher;

float top, right, left, bottom;

float radius;

float yBumperWidth, yBumperHeight, xBumperWidth, xBumperHeight;

float fMorpher, sMorpher;

color rC, lC, bC, tC, nC, ballColor;

float[] xPosBalls = new float[20];

float[] yPosBalls = new float[20];

float lerpNeutral, lerpSpeed;

int rCounter = 00;

int lCounter = 00;

int tCounter = 00;

int bCounter = 00;

void setup()

{

size(800,600);

smooth();

xSpeed = 5.0f;

ySpeed = 5.0f;

lerpNeutral = 0;

lerpSpeed = .1;

for (int i = 0; i < balls; i ++)

{

xPos[i] = width/2;

yPos[i] = height/2;

println (xPos[i]);

}

frameRate(40);

rC = color(242, 68, 68);

lC = color(35,65,240);

bC = color(90,0,180);

tC = color(35,255,18);

nC = color(250,250,250);

ballColor = nC;

}

void draw()

{

background(0);

top = 0;

bottom = height;

left = 0;

right = width;

radius = (width + height)/25;

yBumperWidth = (width + height)/40;

yBumperHeight = (width + height)/15;

xBumperWidth = (width + height)/15;

xBumperHeight = (width + height)/40;

//-------------------------------------------------------------------------theBall

fill(ballColor);

ellipse(xPos[1], yPos[1], (width + height)/25, (width + height)/25);

xPos[1] += xSpeed;

yPos[1] += ySpeed;

//----------------------------------------------------------------------theBumpers

rectMode(CENTER);

fill(lC);

rect(yBumperWidth/2, yPos[1], yBumperWidth, yBumperHeight);

fill(rC);

rect(right-((yBumperWidth)/2), yPos[1], yBumperWidth, yBumperHeight);

fill(tC);

rect(xPos[1], xBumperHeight/2, xBumperWidth, xBumperHeight);

fill(bC);

rect(xPos[1], bottom - (xBumperHeight/2), xBumperWidth, xBumperHeight);

//wallBounce

xPos[1] = constrain(xPos[1], left + radius/2 + yBumperWidth, right - radius/2 - yBumperWidth);

if(xPos[1] >= right - radius/2 - yBumperWidth || xPos[1] <= left + radius/2 + yBumperWidth)

{

xSpeed = -xSpeed;

}

yPos[1] = constrain(yPos[1], top + radius/2 + xBumperHeight, bottom - radius/2 - xBumperHeight);

if(yPos[1] >= bottom - radius/2 - xBumperHeight || yPos[1] <= top + radius/2 + xBumperHeight)

{

ySpeed = -ySpeed;

}

lerpNeutral =+ lerpSpeed;

//colorChanger

//---------------------------------------------------rightChange

if (xPos[1] >= right - radius/2 - yBumperWidth)

{

rCounter += 1;

println("Right Bumper hit = " + rCounter + " times");

}

if ((xPos[1] <= right - radius/2 - yBumperWidth) && (xPos[1] > right - (radius/2) * 6 - yBumperWidth))

{

ballColor = lerpColor(rC, nC, norm(xPos[1], right - radius/2 - yBumperWidth, right - (radius/2) * 6 - yBumperWidth));

}

//----------------------------------------------------leftChange

if (xPos[1] <= left + radius/2 + yBumperWidth)

{

lCounter += 1;

println("Left Bumper hit = " + lCounter + " times");

ballColor = lC;

}

if ((xPos[1] >= left + radius/2 + yBumperWidth) && (xPos[1] <= (left + radius/2) * 6 + yBumperWidth))

{

ballColor = lerpColor(lC, nC, norm(xPos[1], left + radius/2 + yBumperWidth, (left + radius/2) * 6 + yBumperWidth));

}

//---------------------------------------------------bottomChange

if (yPos[1] >= bottom - radius/2 - xBumperHeight)

{

bCounter += 1;

println("Bottom Bumper hit = " + bCounter + " times");

ballColor = bC;

}

if ((yPos[1] <= bottom - radius/2 - xBumperHeight) && (yPos[1] >= bottom - (radius/2) * 6 - xBumperHeight))

{

ballColor = lerpColor(bC, nC, norm(yPos[1], bottom - radius/2 - xBumperHeight, bottom - (radius/2) * 6 - xBumperHeight));

}

//------------------------------------------------------topChange

if (yPos[1] <= top + radius/2 + xBumperHeight)

{

tCounter += 1;

println("Top Bumper hit = " + tCounter + " times");

ballColor = tC;

}

//topFadeEffect

if ((yPos[1] >= top + radius/2 + xBumperHeight) && (yPos[1] <= top + (radius/2) * 6 + xBumperHeight))

{

ballColor = lerpColor(tC, nC, norm(yPos[1], top + radius/2 + xBumperHeight, top + (radius/2) * 6 + xBumperHeight));

}

My problem is, I need to somehow get 19 further ellipses behind the initial ellipse (total:20 on screen) which are a frame behind each other. After doing that, I need to make each ball slowly alpha out till the last one is gone.

I know this is a pretty intense question, but any help in the right direction would be greatly appreciated.

Replies(4)

cedrickie..

Re: How to use a for loop and the array function to create a tail for a bouncing ball

2 years ago

maybe that helps

int count=20;
float[] oldX = new float[count];
float[] oldY = new float[count];

void setup() {
size(400,400);
background(255);
frameRate(40);
smooth();
}

void draw() {

float[] tmpX = new float[count];
float[] tmpY = new float[count];
for(int i=0; i<count-1; i++) {
    tmpX[i+1] = oldX[i];
    tmpY[i+1] = oldY[i];
}
tmpX[0]=mouseX;
tmpY[0]=mouseY;

oldX=tmpX;
oldY=tmpY;

background(255);
noStroke();
for(int i=0; i<count; i++) {

    fill(255,0,0,255-255/count*i);
    ellipse(oldX[i],oldY[i],30,30);
}
}

calsign

Re: How to use a for loop and the array function to create a tail for a bouncing ball

2 years ago

For that, you don't necessarily need to use arrays.

What I would do, the same thing used in the PVector examples (maybe others as well) is perform background(0, alpha) alpha in your case being (255 / 20) for 20 balls in trail. This will also trail everything else on the screen, though, which can be avoided with more tweaking, but this is probably suitable for your purposes.

You would also call background(0) in setup so that the background is initialized.

cedrickie..

Re: How to use a for loop and the array function to create a tail for a bouncing ball

2 years ago

this is no question an easy and quick way to achieve a ghosting/fading effect but there are definitely some cons using it, for example as you mentioned when drawing other objects that shouldnt fade its getting more complicated as you need to draw them into a different buffer for example. but also when you plan to export your drawing as pdf for example you need to do it with an array the same when you dont want to just fade them but also for example scale them cause this cant be achieved by drawing a transparent background.

just a quick note. adding alpha to a background doesnt work.
you have to draw a large rect instead if you want to use this technique

rapatski

Re: How to use a for loop and the array function to create a tail for a bouncing ball

2 years ago

tmpX?

for(int i = 0; i < count-1; i++) {
trailX[i] = trailX[i+1];
trailY[i] = trailY[i+1];
}
trailX[count-1] = mouseX;
trailY[count-1] = mouseY;

Seems to be enough..?

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