FYI
1>..\..\..\OpenSceneGraph\src\osg\KdTree.cpp(108) : warning C4018: '<=' :
signed/unsigned mismatch
James Killian
----- Original Message -----
From: "Robert Osfield" <[EMAIL PROTECTED]>
To: "OpenSceneGraph Submissions" <[email protected]>
Sent: Wednesday, July 16, 2008 6:08 AM
Subject: Re: [osg-submissions] KDTree : intersection
Hi Adrian,
I have gone for the precompute the _d_invX, _d_invY, _d_invZ, this is
now checked in to SVN.
Robert.
On Wed, Jul 16, 2008 at 8:54 AM, Adrian Egli OpenSceneGraph (3D)
<[EMAIL PROTECTED]> wrote:
Hi Robert,
this make sense. the code is not only reordering it's also more robust.
e.x
- s.x can be zero. it means that s.x == e.x , so we can assume that
invDir.x
== 0.0 doesn't destroy our math :-)
have a look at.......
bool KdTree::intersect(const osg::Vec3& start, const osg::Vec3& end,
LineSegmentIntersections& intersections) const
{
...
osg::Vec3 dir(end-start);
const osg::Vec3 invDir(
dir.x() != 0.0f ? 1.0f/dir.x() : 0.0f,
dir.y() != 0.0f ? 1.0f/dir.y() : 0.0f,
dir.z() != 0.0f ? 1.0f/dir.z() : 0.0f
);
if you would prefere a member variable, then we can change it. but take
care
about the fix
_dir_invDiv_x = d.x() == 0.0f ? osg::Vec3f(0.0f,0.0f,0.0f) : _d/_d.x();
_dir_invDiv_y = d.y() == 0.0f ? osg::Vec3f(0.0f,0.0f,0.0f) : _d/_d.y();
_dir_invDiv_z = d.z() == 0.0f ? osg::Vec3f(0.0f,0.0f,0.0f) : _d/_d.z();
****************************************************************************************************
SORRY: i just posted a second kdTree.cpp fix, may we can do this invDir
change in the latest kdTree.cpp
****************************************************************************************************
2008/7/15 Robert Osfield <[EMAIL PROTECTED]>:
Hi Adrian,
I've just do a review of your changes, I now understand what the
optimization do - basically improve the intersectAndClip function.
The changes are a bit awkward and miss a few opportunities to optimize
further. The awkward part come from passing dir and invDir as
parameters, but I can't see anywhere in the code where you are
actually modifying them. Reflecting on the code it looks like we
needn't ever modify them, so dir is in fact just IntersectKdTree::_d,
something that is already precomuted, its only the invDir you are
adding. Moving invDir into the IntersectKdTree as a member would
allow us to avoid passing the dir and invDir as a parameters
completely.
The optimization comes by reordering the maths i.e
My original code:
s = s+(e-s)*(bb.xMin()-s.x())/(e.x()-s.x());
You new code:
s += dir*(bb.xMin()-s.x())*invDir.x();
If we reoder then we have:
s += _dir_invDiv_x * (bb.xMin()-s.x());
Where _dir_invDiv_x = _d/_d.x();
If this makes sense then we can port the code across to use this method.
Robert.
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--
********************************************
Adrian Egli
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