Fixed false positives in the culling system.

This fixes numerous false positives coming out of the culling system.

AABB checks are now a full separating-axis check against the frustum, with the points of the frustum being compared to the planes of the box just as the points of the box were being compared to the planes of the frustum. This fixes large objects behind the camera not being culled correctly.

Some systems that used frustums that were (sometimes mistakenly?) unbounded on one or more side have been modified to be fully enclosed.

core/math/geometry.cpp

@@ -1185,3 +1185,42 @@ Vector<Vector<Point2> > Geometry::_polypath_offset(const Vector<Point2> &p_polyp
 	}
 	return polypaths;
 }
+
+Vector<Vector3> Geometry::compute_convex_mesh_points(const Plane *p_planes, int p_plane_count) {
+
+	Vector<Vector3> points;
+
+	// Iterate through every unique combination of any three planes.
+	for (int i = p_plane_count - 1; i >= 0; i--) {
+		for (int j = i - 1; j >= 0; j--) {
+			for (int k = j - 1; k >= 0; k--) {
+
+				// Find the point where these planes all cross over (if they
+				// do at all).
+				Vector3 convex_shape_point;
+				if (p_planes[i].intersect_3(p_planes[j], p_planes[k], &convex_shape_point)) {
+
+					// See if any *other* plane excludes this point because it's
+					// on the wrong side.
+					bool excluded = false;
+					for (int n = 0; n < p_plane_count; n++) {
+						if (n != i && n != j && n != k) {
+							real_t dp = p_planes[n].normal.dot(convex_shape_point);
+							if (dp - p_planes[n].d > CMP_EPSILON) {
+								excluded = true;
+								break;
+							}
+						}
+					}
+
+					// Only add the point if it passed all tests.
+					if (!excluded) {
+						points.push_back(convex_shape_point);
+					}
+				}
+			}
+		}
+	}
+
+	return points;
+}