Thanks Marcin That's sort of what I was thinking that it had to be rounding, our tiles are localized so YX are relatively small but the Z could be any value range on the earth and seabed, 1million,-1million was over kill for the segment length. Be we will look to go the double route . Thanks again for you reply,
Gordon Product Manager 3d __________________________________________________________ Gordon Tomlinson Email : gtomlinson @ overwatch.textron.com __________________________________________________________ ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Marcin Prus Sent: Wednesday, April 15, 2009 4:01 AM To: OpenSceneGraph Users Subject: Re: [osg-users] Erratic intersections with long line segments Hi Gordon, we had similar problem here. We were standing exactly at the edge of 2 adjacent triangles in large terrain database and osgUtil::LineSegmentIntersector failed because of internal floating precision. Using doubles instead of floats inside osgUtil::LineSegmentIntersector solved our problems. I've made submission on 18.02.2009 with modified LineSegmentIntersector using cmake flag to set float or double precision internally but it never got into the trunk. You can look at it and create your own LineSegmentIntersectorDbl : public LineSegmentIntersector with double maths inside. Perhaps this will help - it did in our case Best, Marcin Prus Tomlinson, Gordon pisze: HI All I posting this for one of my folks who's is having some erratic results when using a long vertical line segment and the standard osgUtil::LineSegmentIntersector Basically when he sets a line segment up with end X,Y, 1000000 and start X,Y, -1000000 , occasionally we fail to get a hit even though we are in the middle of the terrain skin, although moving the X,Y several meters in any direction and we get a hit. If we reduce the Z of the line segment to 500k and -500k this happens less errant fails, if we reduce the Z's to 1k, -1k then we never get a fail, further when we are failing with the intersections if the camera is further away from the intersection the less fails we get, the more we move closer to the intersection point the more fails we get. Our Near and Far clip are fixed, 1 to 10-20k , the terrain skin is stanard OSG geometry, nothing fancy, some lods, but the level and which lod is showing does not seem to be the issue I'm at at a loss to why this may be happening, we are not doing anything out the oridnary in this case that I can think that would cause this erratic behaviour , any one seen anything like this before ? thanks Gordon Product Manager 3d __________________________________________________________ Gordon Tomlinson Email : gtomlinson @ overwatch.textron.com __________________________________________________________ (C): (+1) 571-265-2612 (W): (+1) 703-437-7651 "Self defence is not a function of learning tricks but is a function of how quickly and intensely one can arouse one's instinct for survival" - Master Tambo Tetsura ________________________________ _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- Marcin Prus Kierownik Projektu ________________________________ ETC-PZL Aerospace Industries Sp. z o.o. Al. Krakowska 110/114, P.O. Box 22 02-256 Warszawa http://www.ai.com.pl tel: (48-22) 846-54-17 wew. 135 fax (48-22) 846-54-18 e-mail: [email protected] NIP 522-01-01-817 KRS 0000010025 Sąd Rejonowy dla m. st. Warszawy w Warszawie XIII Wydział Gospodarczy Krajowego Rejestru Sądowego. Wniesiony kapitał zakładowy Spółki wynosi 1 000 000 złotych.
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