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Message #17682
Re: [Question #101686]: cell.intersects() functionality in 0.9.7? (i.e. GTS dependencies)
Garth N. Wells wrote:
Andre Massing wrote:
Question #101686 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/101686
Status: Open => Answered
Andre Massing proposed the following answer:
On Friday 19. February 2010 18.33.47 marc spiegelman wrote:
> New question #101686 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/101686
>
> Hi All,
> I've implemented a rather nifty semi-lagrangian advection scheme in
> dolfin that requires rapid checking to see if a point intersects a
> cell
> (without necessarily firing up the full intersection operator). Pre
> 0.9.7
> this was implemented as cell.intersects(point).
>
> Everything works fine in 0.9.6 with the new CGAL intersection
> operator
> replacing the GTS intersection operator (with about a 20% speedup).
Did you only use the intersection between meshentities and points or did
you
use also the new mesh intersection operator? Just curious, because the
former
code for intersection between points og e.g. triangles did not change.
> However, in 0.9.7 the code breaks because cell.intersects() has been
> removed as a GTS dependency (actually, looking at
> TriangleCell.intersects(point), it looks like it simply reproduces
> GTS
> code but wasn't actually dependent on GTS)
Yep that's true, the intersection functions was removed and there is a new
PrimitiveIntersector class in C++ with two static functions. These computes
the intersection between rather arbitrary mesh entities (exact or only
using
doubling precision). The functions are exposed as do_intersect and
do_intersect_exact in the python interface. But you are right, a point -
meshentity intersection is not provided. I attached a patch against the
recent
0.9.7 release. Could you can apply to you sources and see whether it
works for
you?
Andre: Did you forget to attach it?
Hmm, I did not, at least in my sent box it also appeared with
attachment. Strange... resend it (CC to the DOLFIN-ml).
>
> The question is... is there is any equivalent functionality in CGAL
and is
> anyone interested in implementing it (either as cell.intersects(??)
> or some other interface). The functionality should be straightforward
> (and I'd be surprised if it didn't exist), given a *known cell* and a
> point, does the cell intersect the point. This would be useful for
> particle based methods as well.
>
> On a related note...are there any plans for a parallel implementation
> of Function::eval(Array<double>& values, const Array<double>& x) by
> release 1.0?
I've just pushed a change for this, although it won't work for
off-process points.
Garth
>
> All assistance greatly appreciated
Any feedback as well :)
> marc
>
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=== modified file 'dolfin/mesh/PrimitiveIntersector.cpp'
--- dolfin/mesh/PrimitiveIntersector.cpp 2010-02-11 00:47:11 +0000
+++ dolfin/mesh/PrimitiveIntersector.cpp 2010-02-19 18:39:14 +0000
@@ -6,7 +6,7 @@
// Modified by André Massing, 2010
//
// First added: 2010-02-09
-// Last changed: 2010-02-11
+// Last changed: 2010-02-19
//
//Author: André Massing (am), massing@xxxxxxxxx
//Company: Simula Research Laboratory, Fornebu, Norway
@@ -26,13 +26,22 @@
{
return PrimitiveIntersector::do_intersect_with_kernel<SCK>(entity_1, entity_2);
}
-
+//-----------------------------------------------------------------------------
+bool PrimitiveIntersector::do_intersect(const MeshEntity & entity, const Point & point)
+{
+ return PrimitiveIntersector::do_intersect_with_kernel<SCK>(PrimitiveTraits<PointPrimitive,SCK>::datum(point), entity);
+}
+//-----------------------------------------------------------------------------
bool PrimitiveIntersector::do_intersect_exact(const MeshEntity & entity_1, const MeshEntity & entity_2)
{
-
return PrimitiveIntersector::do_intersect_with_kernel<EPICK>(entity_1, entity_2);
}
//-----------------------------------------------------------------------------
+bool PrimitiveIntersector::do_intersect_exact(const MeshEntity & entity, const Point & point)
+{
+ return PrimitiveIntersector::do_intersect_with_kernel<EPICK>(PrimitiveTraits<PointPrimitive,EPICK>::datum(point), entity);
+}
+//-----------------------------------------------------------------------------
template <typename K, typename T, typename U >
bool PrimitiveIntersector::do_intersect_with_kernel(const T & entity_1, const U & entity_2)
{
=== modified file 'dolfin/mesh/PrimitiveIntersector.h'
--- dolfin/mesh/PrimitiveIntersector.h 2010-02-10 12:25:51 +0000
+++ dolfin/mesh/PrimitiveIntersector.h 2010-02-19 18:17:44 +0000
@@ -6,7 +6,7 @@
// Modified by André Massing, 2010
//
// First added: 2010-02-09
-// Last changed: 2010-02-10
+// Last changed: 2010-02-19
//
//Author: André Massing (am), massing@xxxxxxxxx
//Company: Simula Research Laboratory, Fornebu, Norway
@@ -19,6 +19,7 @@
namespace dolfin
{
class MeshEntity;
+ class Point;
/// This class implements an intersection detection, detecting whether two given (arbitrary) meshentities intersect.
class PrimitiveIntersector
@@ -28,10 +29,12 @@
///kernel which is faster but may suffer from floating point precision
//issues.
static bool do_intersect(const MeshEntity & entity_1, const MeshEntity & entity_2);
+ static bool do_intersect(const MeshEntity & entity_1, const Point & point);
///Computes whether two mesh entities intersect. Uses an exact geometry
///kernel which is slower but detects intersection always correctly.
static bool do_intersect_exact(const MeshEntity & entity_1, const MeshEntity & entity_2);
+ static bool do_intersect_exact(const MeshEntity & entity_1, const Point & point);
private:
//@{
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