PVector Instance(The nature of code)

by jane kim(김해인) 2015.10.11에 작성: Vector개념을 배우고 이를 코드로 작성해 보았습니다..

코드 실행: https://www.khanacademy.org/computer-programming/pvector-instance/6479887750266880

/**

Try to catch the ball! It's harder when you move, but easy when you stay..... :)

Line 37: The reason why I used constrain() is because sometimes(or mostly) when you move your mouse in further directions, the ball can get off the canvas. Making the user a bit fustrated.

So, I just used constrain() to command the code where the ball can go without further ado.(it can only move inside the canvas!)

*/

background(97, 237, 255);

//I'm puting this in a function just in case somebody tweaks this code and gets an error. (Nobody wants that to happen!)

var ball = function(x, y) {

    translate(x, y);

    noStroke();

    fill(255, 0, 0);

    ellipse(0, 0, 30, 30);

    fill(255, 255, 255);

    arc(0, 0, 30, 30, 0, 180);

    fill(0, 0, 0);

    ellipse(0, 0, 5, 5);

};

mouseMoved = function() {

    background(97, 237, 255);

    

    //Creating two new PVectors, mouse and center.

    /* The mouse is a vector showing us where the mouse is, and the center is just the center of the canvas.(In vector scale!) */

    var mouse = new PVector(mouseX, mouseY);

    var center = new PVector(width/2, height/2);

    

    /* The mouse.sub(center) is in order to let the ball to fallow the mouse. Without it, it will go away twice from the position the mouse is currently on.

NOTE: mouse.mult(3) is to make distances from the mouse and the ball 3 times further.*/

    mouse.sub(center);

    mouse.mult(3);

    

    //Since translate() is not with either pushMatrix() or popMatrix(), we have to reset the code by using resetMatrix().

    resetMatrix();

    translate(width/2, height/2);

    ball(constrain(mouse.x, -185, 185), constrain(mouse.y, -185, 185));

};

/**

Note: This is just a practice program for my vector skills, not for khantober!

*/

by jane kim