Replace a non-aligned cuboid with a cylinder in client::ActiveObjectMgr::getActiveSelectableObjects

Author: numberZero

src/client/activeobjectmgr.cpp

@@ -110,17 +110,8 @@ void ActiveObjectMgr::getActiveObjects(const v3f &origin, f32 max_d,
 std::vector<DistanceSortedActiveObject> ActiveObjectMgr::getActiveSelectableObjects(const core::line3d<f32> &shootline)
 {
 	std::vector<DistanceSortedActiveObject> dest;
-	// Imagine a not-axis-aligned cuboid oriented into the direction of the shootline,
-	// with the width of the object's selection box radius * 2 and with length of the
-	// shootline (+selection box radius forwards and backwards). We check whether
-	// the selection box center is inside this cuboid.
-
 	f32 max_d = shootline.getLength();
 	v3f dir = shootline.getVector().normalize();
-	// arbitrary linearly independent vector and orthogonal dirs
-	v3f li2dir = dir + (std::fabs(dir.X) < 0.5f ? v3f(1,0,0) : v3f(0,1,0));
-	v3f dir_ortho1 = dir.crossProduct(li2dir).normalize();
-	v3f dir_ortho2 = dir.crossProduct(dir_ortho1);
 
 	for (auto &ao_it : m_active_objects) {
 		ClientActiveObject *obj = ao_it.second;
@@ -129,23 +120,22 @@ std::vector<DistanceSortedActiveObject> ActiveObjectMgr::getActiveSelectableObje
 		if (!obj->getSelectionBox(&selection_box))
 			continue;
 
-		// possible optimization: get rid of the sqrt here
-		f32 selection_box_radius = selection_box.getRadius();
-
-		v3f pos_diff = obj->getPosition() + selection_box.getCenter() - shootline.start;
+		v3f obj_center = obj->getPosition() + selection_box.getCenter();
+		f32 obj_radius_sq = selection_box.getExtent().getLengthSQ() / 4;
 
-		f32 d = dir.dotProduct(pos_diff);
+		v3f c = obj_center - shootline.start;
+		f32 a = dir.dotProduct(c);           // project c onto dir
+		f32 b_sq = c.getLengthSQ() - a * a;  // distance from shootline to obj_center, squared
 
-		// backward- and far-plane
-		if (d + selection_box_radius < 0.0f || d - selection_box_radius > max_d)
+		if (b_sq > obj_radius_sq)
 			continue;
 
-		// side-planes
-		if (std::fabs(dir_ortho1.dotProduct(pos_diff)) > selection_box_radius
-				|| std::fabs(dir_ortho2.dotProduct(pos_diff)) > selection_box_radius)
+		// backward- and far-plane
+		f32 obj_radius = std::sqrt(obj_radius_sq);
+		if (a < -obj_radius || a > max_d + obj_radius)
 			continue;
 
-		dest.emplace_back(obj, d);
+		dest.emplace_back(obj, a);
 	}
 	return dest;
 }