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collide: Use correct intersection point for sphere into poly

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Previously, the reported surface and intersection points could be outside the polygon if the sphere was colliding with the edge.

Fixes #907
This commit is contained in:
rdb 2020-05-05 16:52:21 +02:00
parent 3598222977
commit 9ad4e4586c
3 changed files with 44 additions and 8 deletions
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46
panda/src/collide/collisionPolygon.cxx
View File

@ -484,6 +484,7 @@ test_intersection_from_sphere(const CollisionEntry &entry) const {
}
LPoint2 p = to_2d(from_center - dist * get_normal());
LPoint2 edge_p;
PN_stdfloat edge_dist = 0.0f;
const ClipPlaneAttrib *cpa = entry.get_into_clip_planes();
@ -492,7 +493,7 @@ test_intersection_from_sphere(const CollisionEntry &entry) const {
Points new_points;
if (apply_clip_plane(new_points, cpa, entry.get_into_node_path().get_net_transform())) {
// All points are behind the clip plane; just do the default test.
edge_dist = dist_to_polygon(p, _points);
edge_dist = dist_to_polygon(p, edge_p, _points);
} else if (new_points.empty()) {
// The polygon is completely clipped.
@ -500,12 +501,12 @@ test_intersection_from_sphere(const CollisionEntry &entry) const {
} else {
// Test against the clipped polygon.
edge_dist = dist_to_polygon(p, new_points);
edge_dist = dist_to_polygon(p, edge_p, new_points);
}
} else {
// No clip plane is in effect. Do the default test.
edge_dist = dist_to_polygon(p, _points);
edge_dist = dist_to_polygon(p, edge_p, _points);
}
// Now we have edge_dist, which is the distance from the sphere center to
@ -548,9 +549,21 @@ test_intersection_from_sphere(const CollisionEntry &entry) const {
into_depth = max_dist - orig_dist;
}
new_entry->set_surface_normal(normal);
if (edge_dist >= 0.0f) {
// If colliding with an edge, we take the point on the edge.
LMatrix4 to_3d_mat;
rederive_to_3d_mat(to_3d_mat);
LPoint3 surface_point = to_3d(edge_p, to_3d_mat);
new_entry->set_surface_point(surface_point);
new_entry->set_interior_point(surface_point - normal * into_depth);
} else {
// Otherwise, we use the projection of the center onto the polygon.
new_entry->set_surface_point(from_center - normal * dist);
new_entry->set_interior_point(from_center - normal * (dist + into_depth));
}
new_entry->set_surface_normal(normal);
new_entry->set_contact_pos(contact_point);
new_entry->set_contact_normal(get_normal());
new_entry->set_t(actual_t);
@ -1330,9 +1343,12 @@ point_is_inside(const LPoint2 &p, const CollisionPolygon::Points &points) const
* Returns the linear distance from the 2-d point to the nearest part of the
* polygon defined by the points vector. The result is negative if the point
* is within the polygon.
*
* If the point is not within the polygon, the closest point to the edge is
* returned in the edge_p argument.
*/
PN_stdfloat CollisionPolygon::
dist_to_polygon(const LPoint2 &p, const CollisionPolygon::Points &points) const {
dist_to_polygon(const LPoint2 &p, LPoint2 &edge_p, const CollisionPolygon::Points &points) const {
// We know that that the polygon is convex and is defined with the points in
// counterclockwise order. Therefore, we simply compare the signed distance
@ -1344,6 +1360,7 @@ dist_to_polygon(const LPoint2 &p, const CollisionPolygon::Points &points) const
bool got_dist = false;
PN_stdfloat best_dist = -1.0f;
size_t best_i;
size_t num_points = points.size();
for (size_t i = 0; i < num_points - 1; ++i) {
@ -1353,6 +1370,7 @@ dist_to_polygon(const LPoint2 &p, const CollisionPolygon::Points &points) const
if (!got_dist || d < best_dist) {
best_dist = d;
got_dist = true;
best_i = i;
}
}
}
@ -1363,6 +1381,24 @@ dist_to_polygon(const LPoint2 &p, const CollisionPolygon::Points &points) const
if (!got_dist || d < best_dist) {
best_dist = d;
got_dist = true;
best_i = num_points - 1;
}
}
if (got_dist) {
// Project the point onto the best line, so that we can confine it to the
// line segment.
LPoint2 best_p = points[best_i]._p;
LPoint2 next_p = points[(best_i + 1) % points.size()]._p;
LVector2 segment = next_p - best_p;
PN_stdfloat t = (p - best_p).dot(segment) / segment.length_squared();
if (t <= 0.0f) {
edge_p = best_p;
} else if (t >= 1.0f) {
edge_p = next_p;
} else {
LVector2 v(points[best_i]._v[1], -points[best_i]._v[0]);
edge_p = p - v * best_dist;
}
}

2
panda/src/collide/collisionPolygon.h
View File

@ -124,7 +124,7 @@ private:
const Points &points) const;
bool point_is_inside(const LPoint2 &p, const Points &points) const;
PN_stdfloat dist_to_polygon(const LPoint2 &p, const Points &points) const;
PN_stdfloat dist_to_polygon(const LPoint2 &p, LPoint2 &edge_p, const Points &points) const;
void project(const LVector3 &axis, PN_stdfloat &center, PN_stdfloat &extent) const;
void setup_points(const LPoint3 *begin, const LPoint3 *end);

2
tests/collide/test_into_poly.py
View File

@ -31,7 +31,7 @@ def test_sphere_into_poly():
# Colliding just on the edge
entry, np_from, np_into = make_collision(CollisionSphere(0, 0, 3, 2), poly)
assert entry.get_surface_point(np_from) == Point3(0, 0, 3)
assert entry.get_surface_point(np_from) == Point3(0, 0, 1)
assert entry.get_surface_normal(np_into) == Vec3(-1, 0, 0) # Testing surface normal
# No collision