Acceleration doesn't affect Velocity

Programming Questions

timi19

Acceleration doesn't affect Velocity

in Programming Questions • 2 months ago

Hello

Im just working on Daniel Shiffman's Nature of Code book and I have the following problem with the exercise 1.8.

I have an object (ellipse) which should move towards the cursor mouse. My Problem is now that I don't know how to control the speed of my object. The object should move faster when it is farther away but my object is just keeping the same speed all the time. How can i control this by changing only the acceleration? I know it has to do something with the distance between these two points.

Here is my small update Code in my object:

void update() {
PVector mouse = new PVector(mouseX, mouseY);
PVector dir = PVector.sub(mouse, location);
float mag = dir.mag();
dir.normalize(); //now we have just the direction to the mouse
acceleration = dir;
velocity.add(acceleration);
velocity.limit(3);
location.add(velocity);
}

Replies(3)

asimes

Re: Acceleration doesn't affect Velocity

2 months ago

The way I learned to do it is like Zeno's arrow, cut the distance between the point and the target in half. If you want the point to move slower, cut the distance by a smaller amount (arbitraryNumber = 4.0 means distance is cut by a quarter).

PVector ball;
float arbitraryNumber = 4.0; // Make this bigger to slow down the ball
void setup() {
size(600, 600);
noStroke();
fill(255, 0, 0);
ball = new PVector(width/2, height/2);
}
void draw() {
background(0);
ellipse(ball.x, ball.y, 50, 50);
if (ball.x < mouseX) ball.x += (mouseX-ball.x)/arbitraryNumber;
if (ball.x > mouseX) ball.x -= (ball.x-mouseX)/arbitraryNumber;
if (ball.y < mouseX) ball.y += (mouseY-ball.y)/arbitraryNumber;
if (ball.y > mouseX) ball.y -= (ball.y-mouseY)/arbitraryNumber;
}

timi19

Re: Acceleration doesn't affect Velocity

2 months ago

Thank you for your reply. But im working on a solution with changing the velocity and acceleration. I have to reach that the acceleration will reach 0 when moving towards my mouse. Does anybody know a solution by changing just the acceleration?

amnon.owed

Re: Acceleration doesn't affect Velocity

2 months ago

You can use the magnitude of the direction vector, which is the distance between the two positions. Within a certain distance map the acceleration from max to 0. Currently you don't really use a max, but you do normalize(), so the implicit max is 1.

Adapted Code

void update() {
PVector mouse = new PVector(mouseX, mouseY);
PVector dir = PVector.sub(mouse, location);
float mag = dir.mag();
// dir.normalize(); //now we have just the direction to the mouse
float max = 1;
float withinDistance = 25;
if (mag < withinDistance) {
dir.setMag( map(mag, 0, withinDistance, 0, max) );
} else {
dir.setMag(max);
}
acceleration = dir;
velocity.add(acceleration);
velocity.limit(3);
location.add(velocity);
}