Jumping realistic in Processing with PVectors - processing

Question

I tried to make a jump look realistic, while I watched through the Videos:
The Natur of Code - The Coding Train
I got into PVectors. I strongly recomend watching him. But to get to my question, everything seems to work, exept that it draws the rectangle (my PVector) the way I want.
void keyPressed() {
if (keyCode == UP) {
for (int i = 0; i < 16; i++) {
location.sub(velocity);
velocity.sub(acceleration);
h.display();
background(0);
}
velocity.set(0, 15);
}
}
That's the Code, I expect it to "jump", but nothing realy happens. You can see that the rectangle get's drawn again (on the same spot), but there's no movement. It's definitly an issue with the drawing of the background or something, I don't know what exaclty though.

Answer 1

The nature of your question is unclear. You mentioned issues regarding the background interfering with your rectangle after the UP arrow key is pressed. This is likely because background(0) is called immediately after h.display(). I would remove background(0) from your loop if it's a display issue.
Other than that, there seem to be other issues with the loop itself. When the UP key is pressed, h is affected by acceleration only for 16 frames. To make your object more realistic, gravity (or whatever acceleration you choose) should constantly be acting upon the object.
With that in mind, here's a solution for you.
void keyPressed() {
if (keyCode == UP) {
// Make the character 'jump' upwards when the UP arrow is pressed.
// Setting the velocity should be the only thing happening when the key is pressed.
velocity.set(0, -2);
}
}
void draw() {
// Reset the background each frame so rectangles don't overlap.
background(255);
// Always draw the rectangle AFTER resetting the canvas.
h.display();
// Change the object's location by it's velocity.
location.add(velocity);
// And chance the object's velocity by it's acceleration.
// Since acceleration is the acting force of gravity in this situation, acceleration need not be changed.
velocity.add(acceleration);
// Prevent the rectangle from falling through the bottom of the canvas.
if(location.y > height - 5) location.y = height - 5;
}
// You negleteced to define your variables in your code snippet. Here they are.
PVector location = new PVector(0, 0);
PVector velocity = new PVector(0, 0);
PVector acceleration = new PVector(0, 0.1); // Notice that acceleration's y-value is 0.01. This is so you can see the effect of gravity.
// Define your rectangle object.
Object h = new Object();
class Object {
Object() {} // Constructor.
void display() {
// Draw the rectangle at the x- and y-positions of the location vector.
// The '+ width/2' places it at the center of the screen.
rectMode(CENTER);
rect(location.x + width/2, location.y, 10, 10);
}
}