Hi,

I am building a map drawing app and I want to draw train tracks on the map (a line with intersecting perpendicular lines), but I'm having trouble with the math. I know that I need to do some Pmouse calculations to rotate and space the lines properly, but I haven't done this kind of math in ages. My two problems are:

1. I don't know how to rotate the perpendicular lines with the mouse direction.
2. I don't know how to space the perpendicular lines evenly (every 5px, for example).

Any help is appreciated. Thanks in advance.

float x;
float y;
float px, targetX;
float py, targetY;
float easing = 0.4;
float weight = 2;
color drawColor = 0;

void setup () {
  size(400, 400);
}

void draw() {
  // Free hand line drawing -----------------------------------------//
  strokeWeight(weight);
  stroke(drawColor);
  if (!mousePressed) {
    x = mouseX;
    y = mouseY;
    px = mouseX;
    py = mouseY;
  }
  if (mousePressed) {
    targetX = mouseX;
    float dx = targetX - x;
    if (abs(dx) > 1) {
      x+= dx* easing;
    }
    targetY = mouseY;
    float dy = targetY - y;
    if (abs(dy) > 1) {
      y += dy * easing;
    }
    line(px, py, x, y);
    float tx = (mouseX + cos(QUARTER_PI)*5);
    float ty = (mouseY + sin(QUARTER_PI)*5);
    float bx = (mouseX + cos(-QUARTER_PI)*5);
    float by = (mouseY + sin(-QUARTER_PI)*5);
    strokeWeight(1);
    line(tx, ty, bx, by);
  }
  py = y;
  px = x;
}