toxi::geom::Vec2D toxi::geom::Polygon2D::getCentroid()
{
Vec2D res = Vec2D();
for (int i = 0, num = vertices.size(); i < num; i++)
{
Vec2D a = vertices.at(i);
Vec2D b = vertices.at( ( i + 1 ) % num );
double crossP = a.getX() * b.getY() - b.getX() * a.getY();
res.set( res.getX() + (a.getX() + b.getX()) * crossP, res.getY() + (a.getY() + b.getY()) * crossP );
}
return res.scale(1 / (6 * getArea()));
}
bool toxi::geom::Polygon2D::toOutLine()
{
int corners = vertices.size();
int maxSegs = corners * 3;
std::vector<Vec2D> newVerts;
std::vector< Vec2D > segments( maxSegs );
std::vector< Vec2D > segEnds( maxSegs );
std::vector< double > segAngles( maxSegs );
//Vec2D * segments;
//segments = ( Vec2D* ) malloc( sizeof( Vec2D ) * maxSegs);
//Vec2D * segEnds;
//segEnds = (Vec2D * ) malloc(sizeof( Vec2D ) * maxSegs );
//float * segAngles;
//segAngles = (float * ) malloc( sizeof( float ) * maxSegs );
//Vec2D[] segments = new Vec2D[maxSegs];
//Vec2D[] segEnds = new Vec2D[maxSegs];
//float[] segAngles = new float[maxSegs];
Vec2D start = vertices.at(0);
double lastAngle = toxi::math::MathUtils::PI;
float a, b, c, d, e, f;
double angleDif, bestAngleDif;
int i, j = corners - 1, segs = 0;
if (corners > maxSegs) {
return false;
}
// 1,3. Reformulate the polygon as a set of line segments, and choose a
// starting point that must be on the perimeter.
for (i = 0; i < corners; i++) {
Vec2D pi = vertices.at(i);
Vec2D pj = vertices.at(j);
if (!( pi == pj )) {
segments[segs] = pi;
segEnds[segs++] = pj;
}
j = i;
if (pi.getY() > start.getY() || (pi.getY() == start.getY() && pi.getX() < start.getX())) {
start.set( pi);
}
}
if (segs == 0) {
return false;
}
// 2. Break the segments up at their intersection points.
for (i = 0; i < segs - 1; i++) {
for (j = i + 1; j < segs; j++) {
Line2D li = toxi::geom::Line2D( segments[i], segEnds[i]);
Line2D lj = toxi::geom::Line2D( segments[j], segEnds[j]);
LineIntersection isec = li.intersectLine( lj );
if (isec.getType() == toxi::geom::LineIntersection::Type::INTERSECTING) {
Vec2D ipos = isec.getPos();
if (!( ipos == segments[i] ) && !( ipos == segEnds[i])) {
if (segs == maxSegs) {
return false;
}
segments[segs] = segments[i];
segEnds[segs++] = ipos;
segments[i] = ipos;
}
if (!( ipos == segments[j] ) && !( ipos == segEnds[ j ] ) ) {
if (segs == maxSegs) {
return false;
}
segments[segs] = segments[j];
segEnds[segs++] = ipos;
segments[j] = ipos;
}
}
}
}
// Calculate the angle of each segment.
for (i = 0; i < segs; i++) {
segAngles[i] = segEnds[i].sub( segments[i] ).positiveHeading();
}
// 4. Build the perimeter polygon.
c = static_cast< float > ( start.getX() );
d = static_cast< float > ( start.getY() );
a = c - 1;
b = d;
e = 0;
f = 0;
newVerts.push_back(Vec2D(c, d));
corners = 1;
while (true) {
bestAngleDif = toxi::math::MathUtils::TWO_PI;
for (i = 0; i < segs; i++) {
if (segments[i].getX() == c && segments[i].getY() == d
&& (segEnds[i].getX() != a || segEnds[i].getY() != b)) {
angleDif = lastAngle - segAngles[i];
while (angleDif >= toxi::math::MathUtils::TWO_PI) {
angleDif -= toxi::math::MathUtils::TWO_PI;
}
while (angleDif < 0) {
angleDif += toxi::math::MathUtils::TWO_PI;
}
if (angleDif < bestAngleDif) {
bestAngleDif = angleDif;
e = static_cast< float > ( segEnds[i].getX() );
f = static_cast< float > ( segEnds[i].getY() );
}
}
if (segEnds[i].getX() == c && segEnds[i].getY() == d
&& (segments[i].getX() != a || segments[i].getY() != b)) {
angleDif = lastAngle - segAngles[i] + toxi::math::MathUtils::PI;
while (angleDif >= toxi::math::MathUtils::TWO_PI) {
angleDif -= toxi::math::MathUtils::TWO_PI;
}
while (angleDif < 0) {
angleDif += toxi::math::MathUtils::TWO_PI;
}
if (angleDif < bestAngleDif) {
bestAngleDif = angleDif;
e = static_cast< float > ( segments[i].getX() );
f = static_cast< float > ( segments[i].getY() );
}
}
}
if (corners > 1 && c == newVerts.at(0).getX() && d == newVerts.at(0).getY()
&& e == newVerts.at(1).getX() && f == newVerts.at(1).getY()) {
corners--;
vertices = newVerts;
return true;
}
if (bestAngleDif == toxi::math::MathUtils::TWO_PI || corners == maxSegs) {
return false;
}
lastAngle -= bestAngleDif + toxi::math::MathUtils::PI;
newVerts.push_back(Vec2D(e, f));
corners++;
a = c;
b = d;
c = e;
d = f;
}
}
