Re: [osg-users] BUG REPORT: LineSegmentIntersector
Hi Sean, On Thu, Mar 25, 2010 at 7:34 PM, Sean Spicer sean.spi...@aqumin.com wrote: I came across a nasty little bug today: (a) Create an osg::Geometry and assign a vertex array that is an osg::Vec4Array (b) Try to pick with a LineSegmentIntersector (c) CRASH Ouch. Digging a little bit, it looks like LineSegmentIntersector assumes that vertex arrays are always of type osg::Vec3Array. Are there any plans to change this ? It looks like a tedious, but not terribly invasive change. I don't personally have plans right now, Vec3Array is the usual way to handle vertex data in OSG/OpenGL. The code certainly shouldn't crash though and we need to address this right away. Handling other data types for vertices would be one better than just fixing the crash. I'm open to suggestions, especially if others are willing to pitch in and help code them up ;-) Robert. ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
[osg-users] BUG REPORT: LineSegmentIntersector
I came across a nasty little bug today: (a) Create an osg::Geometry and assign a vertex array that is an osg::Vec4Array (b) Try to pick with a LineSegmentIntersector (c) CRASH Digging a little bit, it looks like LineSegmentIntersector assumes that vertex arrays are always of type osg::Vec3Array. Are there any plans to change this ? It looks like a tedious, but not terribly invasive change. sean _ Sean Spicer Executive Vice President Chief Technology Officer Aqumin (www.aqumin.com) Office+1.713.781.2121 Mobile...+1.713.447.2706 Fax...+1.713.781.2123 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] BUG REPORT: LineSegmentIntersector
Sean Spicer wrote: I came across a nasty little bug today: (a) Create an osg::Geometry and assign a vertex array that is an osg::Vec4Array (b) Try to pick with a LineSegmentIntersector (c) CRASH Digging a little bit, it looks like LineSegmentIntersector assumes that vertex arrays are always of type osg::Vec3Array. Are there any plans to change this ? It looks like a tedious, but not terribly invasive change. Interesting find, Sean... My first reaction is, Why would you ever use a Vec4Array for vertex coordinates?!, but an equally valid counter-argument would be that OpenGL allows 4-element vertices them, so OSG should support them. Next, you have to ask how to intersect a line segment with a geometry with Vec4Array vertices. Would you have to do the w-divide on the vertices before you did the intersection tests to be correct, or is it more correct to not do it, or do you have to do the modelview transform, then the w-divide, then the intersection... Then, you have to start wondering if there are any other assumptions like this being made anywhere (I found other possible cases in Tessellator and Optimizer, though it looks as if they just bail out instead of crashing when they don't find a Vec3Array). I think you may have opened a can of worms here :-) --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] BUG REPORT: LineSegmentIntersector
Without giving away too much IP, one of the reasons why one might want to think about using Vec4Arrays is to take advantage of host-side SIMD operations - which commonly use 128bit registers (4 floats). I agree, this is a can of worms. sean _ Sean Spicer Executive Vice President Chief Technology Officer Aqumin (www.aqumin.com) Office+1.713.781.2121 Mobile...+1.713.447.2706 Fax...+1.713.781.2123 On Thu, Mar 25, 2010 at 2:53 PM, Jason Daly jd...@ist.ucf.edu wrote: Sean Spicer wrote: I came across a nasty little bug today: (a) Create an osg::Geometry and assign a vertex array that is an osg::Vec4Array (b) Try to pick with a LineSegmentIntersector (c) CRASH Digging a little bit, it looks like LineSegmentIntersector assumes that vertex arrays are always of type osg::Vec3Array. Are there any plans to change this ? It looks like a tedious, but not terribly invasive change. Interesting find, Sean... My first reaction is, Why would you ever use a Vec4Array for vertex coordinates?!, but an equally valid counter-argument would be that OpenGL allows 4-element vertices them, so OSG should support them. Next, you have to ask how to intersect a line segment with a geometry with Vec4Array vertices. Would you have to do the w-divide on the vertices before you did the intersection tests to be correct, or is it more correct to not do it, or do you have to do the modelview transform, then the w-divide, then the intersection... Then, you have to start wondering if there are any other assumptions like this being made anywhere (I found other possible cases in Tessellator and Optimizer, though it looks as if they just bail out instead of crashing when they don't find a Vec3Array). I think you may have opened a can of worms here :-) --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] BUG REPORT: LineSegmentIntersector
Looking at osg::State::setVertexPointer(const Array *array), I see that the stride parameter is always 0. If we relaxed this constraint, and allowed an Array to have a stride, I might be able to overcome the problem I am working on. Any comments on what impact this might have ? Also, in order to accomplish what I'm after, I'd need a mechanism to allocate the underlying array on a 16 byte boundary. It looks as if this should be easily doable as MixinVector is a std::vector. Any thoughts on this? sean _ Sean Spicer Executive Vice President Chief Technology Officer Aqumin (www.aqumin.com) Office+1.713.781.2121 Mobile...+1.713.447.2706 Fax...+1.713.781.2123 On Thu, Mar 25, 2010 at 3:05 PM, Sean Spicer sean.spi...@aqumin.com wrote: Without giving away too much IP, one of the reasons why one might want to think about using Vec4Arrays is to take advantage of host-side SIMD operations - which commonly use 128bit registers (4 floats). I agree, this is a can of worms. sean _ Sean Spicer Executive Vice President Chief Technology Officer Aqumin (www.aqumin.com) Office+1.713.781.2121 Mobile...+1.713.447.2706 Fax...+1.713.781.2123 On Thu, Mar 25, 2010 at 2:53 PM, Jason Daly jd...@ist.ucf.edu wrote: Sean Spicer wrote: I came across a nasty little bug today: (a) Create an osg::Geometry and assign a vertex array that is an osg::Vec4Array (b) Try to pick with a LineSegmentIntersector (c) CRASH Digging a little bit, it looks like LineSegmentIntersector assumes that vertex arrays are always of type osg::Vec3Array. Are there any plans to change this ? It looks like a tedious, but not terribly invasive change. Interesting find, Sean... My first reaction is, Why would you ever use a Vec4Array for vertex coordinates?!, but an equally valid counter-argument would be that OpenGL allows 4-element vertices them, so OSG should support them. Next, you have to ask how to intersect a line segment with a geometry with Vec4Array vertices. Would you have to do the w-divide on the vertices before you did the intersection tests to be correct, or is it more correct to not do it, or do you have to do the modelview transform, then the w-divide, then the intersection... Then, you have to start wondering if there are any other assumptions like this being made anywhere (I found other possible cases in Tessellator and Optimizer, though it looks as if they just bail out instead of crashing when they don't find a Vec3Array). I think you may have opened a can of worms here :-) --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] BUG REPORT: LineSegmentIntersector
Sean Spicer wrote: Without giving away too much IP, one of the reasons why one might want to think about using Vec4Arrays is to take advantage of host-side SIMD operations - which commonly use 128bit registers (4 floats). I agree, this is a can of worms. Mmmm, yes, I suppose that would be a compelling reason. --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
