Line Rect Intersect

​

float lineX1 = 50;

float lineY1 = 100;

float lineX2;

float lineY2;

​

float rectX = 100;

float rectY = 90;

float rectWidth = 200;

float rectHeight = 90;

​

void setup() {

  size(400, 400); 

  ellipseMode(RADIUS);

  smooth();

}

​

void draw() {

  background(204);

​

  lineX2 = mouseX;

  lineY2 = mouseY + 60;

  lineX1 = width-mouseX;

  lineY1 = height-mouseY + 60;

​

  if (lineRectangleIntersect(lineX1, lineY1, lineX2, lineY2, rectX, rectY, rectWidth, rectHeight) == true) {

    fill(0); 

  } 

  else {

    fill(255); 

  }

​

  line(lineX1, lineY1, lineX2, lineY2);

  rect(rectX, rectY, rectWidth, rectHeight);

​

}

​

// Code from Seb Lee-Delisle:

// http://sebleedelisle.com/2009/05/super-fast-trianglerectangle-intersection-test/

​

boolean lineRectangleIntersect(float x1, float y1, float x2, float y2, 

                               float rx, float ry, float rw, float rh) {

  float topIntersection;

  float bottomIntersection;

  float topPoint;

  float bottomPoint;

​

  // Calculate m and c for the equation for the line (y = mx+c)

  float m = (y2-y1) / (x2-x1);

  float c = y1 -(m*x1);

​

  // If the line is going up from right to left then the top intersect point is on the left

  if(m > 0) {

    topIntersection = (m*rx  + c);

    bottomIntersection = (m*(rx+rw)  + c);

  }

  // Otherwise it's on the right

  else {

    topIntersection = (m*(rx+rw)  + c);

    bottomIntersection = (m*rx  + c);

  }

​

  // Work out the top and bottom extents for the triangle

  if(y1 < y2) {

    topPoint = y1;

    bottomPoint = y2;

  } else {

    topPoint = y2;

    bottomPoint = y1;

  }

​

  float topOverlap;

  float botOverlap;

​

  // Calculate the overlap between those two bounds

  topOverlap = topIntersection > topPoint ? topIntersection : topPoint;

  botOverlap = bottomIntersection < bottomPoint ? bottomIntersection : bottomPoint;

​

  return (topOverlap<botOverlap) && (!((botOverlap<ry) || (topOverlap>ry+rh)));

​

}

​

​

​

​