CollisionResult GD_API PolygonCollisionTest(Polygon2d& p1,
Polygon2d& p2,
bool ignoreTouchingEdges) {
if (p1.vertices.size() < 3 || p2.vertices.size() < 3) {
CollisionResult result;
result.collision = false;
result.move_axis.x = 0.0f;
result.move_axis.y = 0.0f;
return result;
}
p1.ComputeEdges();
p2.ComputeEdges();
sf::Vector2f edge;
sf::Vector2f move_axis(0, 0);
sf::Vector2f mtd(0, 0);
float min_dist = FLT_MAX;
CollisionResult result;
// Iterate over all the edges composing the polygons
for (std::size_t i = 0; i < p1.vertices.size() + p2.vertices.size(); i++) {
if (i < p1.vertices.size()) // or <=
{
edge = p1.edges[i];
} else {
edge = p2.edges[i - p1.vertices.size()];
}
sf::Vector2f axis(
-edge.y, edge.x); // Get the axis to which polygons will be projected
normalise(axis);
float minA = 0;
float minB = 0;
float maxA = 0;
float maxB = 0;
project(axis, p1, minA, maxA);
project(axis, p2, minB, maxB);
float dist = distance(minA, maxA, minB, maxB);
if (dist > 0.0f || (dist == 0.0 && ignoreTouchingEdges)) {
// If the projections on the axis do not overlap, then
// there is no collision
result.collision = false;
result.move_axis.x = 0.0f;
result.move_axis.y = 0.0f;
return result;
}
float absDist = std::abs(dist);
if (absDist < min_dist) {
min_dist = absDist;
move_axis = axis;
}
}
result.collision = true;
sf::Vector2f d = p1.ComputeCenter() - p2.ComputeCenter();
if (dotProduct(d, move_axis) < 0.0f) move_axis = -move_axis;
result.move_axis = move_axis * min_dist;
return result;
}
RaycastResult GD_API PolygonRaycastTest(
Polygon2d& poly, float startX, float startY, float endX, float endY) {
RaycastResult result;
result.collision = false;
if (poly.vertices.size() < 2) {
return result;
}
poly.ComputeEdges();
sf::Vector2f p, q, r, s;
float minSqDist = FLT_MAX;
// Ray segment: p + t*r, with p = start and r = end - start
p.x = startX;
p.y = startY;
r.x = endX - startX;
r.y = endY - startY;
for (int i = 0; i < poly.edges.size(); i++) {
// Edge segment: q + u*s
q = poly.vertices[i];
s = poly.edges[i];
sf::Vector2f deltaQP = q - p;
float crossRS = crossProduct(r, s);
float t = crossProduct(deltaQP, s) / crossRS;
float u = crossProduct(deltaQP, r) / crossRS;
// Collinear
if (abs(crossRS) <= 0.0001 && abs(crossProduct(deltaQP, r)) <= 0.0001) {
// Project the ray and the edge to work on floats, keeping linearity
// through t
sf::Vector2f axis(r.x, r.y);
normalise(axis);
float rayA = 0.0f;
float rayB = dotProduct(axis, r);
float edgeA = dotProduct(axis, deltaQP);
float edgeB = dotProduct(axis, deltaQP + s);
// Get overlapping range
float minOverlap = std::max(std::min(rayA, rayB), std::min(edgeA, edgeB));
float maxOverlap = std::min(std::max(rayA, rayB), std::max(edgeA, edgeB));
if (minOverlap > maxOverlap) {
return result;
}
result.collision = true;
// Zero distance ray
if (rayB == 0.0f) {
result.closePoint = p;
result.closeSqDist = 0.0f;
result.farPoint = p;
result.farSqDist = 0.0f;
}
float t1 = minOverlap / abs(rayB);
float t2 = maxOverlap / abs(rayB);
result.closePoint = p + t1 * r;
result.closeSqDist = t1 * t1 * (r.x * r.x + r.y * r.y);
result.farPoint = p + t2 * r;
result.farSqDist = t2 * t2 * (r.x * r.x + r.y * r.y);
return result;
} else if (crossRS != 0 && 0 <= t && t <= 1 && 0 <= u && u <= 1) {
sf::Vector2f point = p + t * r;
float sqDist = (point.x - startX) * (point.x - startX) +
(point.y - startY) * (point.y - startY);
if (sqDist < minSqDist) {
if (!result.collision) {
result.farPoint = point;
result.farSqDist = sqDist;
}
minSqDist = sqDist;
result.closePoint = point;
result.closeSqDist = sqDist;
result.collision = true;
} else {
result.farPoint = point;
result.farSqDist = sqDist;
}
}
}
return result;
}
