rotate a line through fixed point

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bob2003

rotate a line through fixed point

in General Discussion • Other • 9 months ago

Hello everyone,

I am quite new in processing programming. I want to create a line that rotates through a fixed point (see the picture below). I want to move the red dot with the mouse (so in need the mouseX and mouseY coordinates in the line coordinates) and the lower end of the line should move in the opposite side at the same time. I tried to create the long line with two seperate lines but then the opposite moving did not work.

Do you have any code tips?

Thanks

And here is my "idea" as a picture

Replies(2)

quarks

Re: rotate a line through fixed point

9 months ago

Try the sketch code below. It provides all the maths needed to do what you want.

float pivotX, pivotY,sx,sy;
float angle, len;
void setup(){
size(300,300);
cursor(CROSS);
pivotX = width/2;
pivotY = height/2;
ellipseMode(CENTER);
}
void draw(){
background(255);
noStroke();
fill(200,200,255);
ellipse(pivotX, pivotY,16,16);
// now calculate line
angle = atan2(mouseY - pivotY, mouseX - pivotX);
len = dist(mouseX,mouseY,pivotX,pivotY);
sx = pivotX - len * cos(angle);
sy = pivotY - len * sin(angle);
stroke(255,0,0);
line(sx,sy,mouseX,mouseY);
noStroke();
fill(255,0,0);
ellipse(mouseX, mouseY,8,8);
}

bob2003

Re: rotate a line through fixed point

9 months ago

Thanks I think this will help

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