bool check_collision_line(Line line1, Line line2) {
bool v1 = false, v2 = false; // vertical lines
if (line1.x1 == line1.x2) {
v1 = true;
}
if (line2.x1 == line2.x2) {
v2 = true;
}
double m1 = 0.0, m2 = 0.0;
double b1 = 0.0, b2 = 0.0;
if (!v1) {
m1 = (line1.y2-line1.y1) / (line1.x2-line1.x1); // Slope
b1 = line1.y1 - m1*line1.x1; // y-intercept
}
if (!v2) {
m2 = (line2.y2-line2.y1) / (line2.x2-line2.x1);
b2 = line2.y1 - m2*line2.x1;
}
if ((v1 ^ v2) == 0) { // either both or none are vertical
if (m1 == m2) {
if (b1 == b2) { // same line
if (v1) {
return check_collision_aligned_line(line1, line2);
} else {
return true;
}
} else {
return false;
}
}
} else if (v1) {
if (is_between(line1.x1, line2.x1, line2.x2)) {
double cy = m2*line1.x1 + b2;
if (is_between(cy, line1.y1, line1.y2)) {
return true;
}
}
return false;
} else if (v2) {
if (is_between(line2.x1, line1.x1, line1.x2)) {
double cy = m1*line2.x1 + b1;
if (is_between(cy, line2.y1, line2.y2)) {
return true;
}
}
return false;
}
double cx = (b2-b1) / (m1-m2); // Possible collision
if (is_between(cx, line1.x1, line1.x2)) {
if (is_between(cx, line2.x1, line2.x2)) {
return true;
}
}
return false;
}
/*
* check_collision_line() - Return whether the given lines intersect
* @line1: one of the lines
* @line2: the other line
*/
bool check_collision_line(const Line& line1, const Line& line2) {
// Check whether either of the given lines are vertical
bool v1 = false, v2 = false;
if (line1.x1 == line1.x2) {
v1 = true;
}
if (line2.x1 == line2.x2) {
v2 = true;
}
// If a given line isn't vertical, then compute its slope and y-intercept
double m1 = 0.0, m2 = 0.0; // Declare slopes
double b1 = 0.0, b2 = 0.0; // Declare y-intercepts
if (!v1) {
m1 = (line1.y2-line1.y1) / (line1.x2-line1.x1);
b1 = line1.y1 - m1*line1.x1;
}
if (!v2) {
m2 = (line2.y2-line2.y1) / (line2.x2-line2.x1);
b2 = line2.y1 - m2*line2.x1;
}
if ((v1 ^ v2) == 0) { // If either both or none of the given lines are vertical
if (m1 == m2) { // If they have the same slope and the same y-intercept then they are the same line
if (b1 == b2) {
if (v1) { // If the lines are vertical then check the collision externally
return check_collision_aligned_line(line1, line2);
} else {
return true; // Return true if the lines are the same line
}
} else {
return false; // Return false if they have the same slope but different y-intercept
}
}
} else if (v1) { // If only the first line is vertical then check whether their bounds line up
if (is_between(line1.x1, line2.x1, line2.x2)) { // Check the vertical line's x-value
double cy = m2*line1.x1 + b2;
if (is_between(cy, line1.y1, line1.y2)) { // Check the non-vertical line's y-value
return true;
}
}
return false;
} else if (v2) { // If only the first line is vertical then check whether their bounds line up
if (is_between(line2.x1, line1.x1, line1.x2)) { // Check the vertical line's x-value
double cy = m1*line2.x1 + b1;
if (is_between(cy, line2.y1, line2.y2)) { // Check the non-vertical line's y-value
return true;
}
}
return false;
}
// If no lines are vertical then check for intercepts otherwise
double cx = (b2-b1) / (m1-m2); // Declare a possible collision, see below math
/*
y1 = m1*x1 + b1
y2 = m2*x2 + b2
for y1 == y2
m1*x1 + b1 = m2*x2 + b2
m1*x1 - m2*x2 = b2 - b1
for cx == x1 == x2
cx*(m1-m2) = (b2-b1)
cx = (b2-b1)/(m1-m2)
*/
if (is_between(cx, line1.x1, line1.x2)) { // Check whether the x-value is within the bounds of both lines
if (is_between(cx, line2.x1, line2.x2)) {
return true; // Return true if there is a collision
}
}
return false; // Return false if there is no collision
}
