[osg-users] question about drawing/modifying lines in OpenSceneGraph

Nguyen Tien Dat tiendatbk at gmail.com
Fri Nov 6 13:59:57 PST 2009


Dear Jeremy,
osgCairo sounds very interesting. Is that a new component of OSG. I
don't see it in my OSG 2.8.2 folder.
One more question, that if you draw a large transparent image with
size 2560x1024, does it affect your frame rate?
Thanks,
Dat

On Fri, Nov 6, 2009 at 3:52 PM, Jeremy Moles <jeremy at emperorlinux.com> wrote:
> On Fri, 2009-11-06 at 15:39 -0600, Nguyen Tien Dat wrote:
>> Dear all,
>> I use the line as a tool to select an object in the scene. I want to
>> implement a kind of "laser pointer" in which user controls the
>> direction of the line by a Wiimote. So the line must be visible to
>> user, and I don't think the one I have now is good enough. I'll change
>> the color and the width to see how it works.
>> Thank all,
>> Dat
>
> Well, if you need high quality vector lines, I would be able to help you
> do that using osgCairo. Basically, what you'd do is use osgCairo to draw
> a number of large, completely transparent images tiled over your scene
> (a grid of 256x256 or 512x512 or whatever).
>
> Then, as you determine the 3D coordinates your lines exist in, you can
> flatten those coordinates into 2D, pass them to cairo, osgCairo will
> updated the textures as you drawn, and in the end you get some very
> nice, high-quality vector lines in whatever style and color you want.
>
> I only mention this because it would be fun to do. :)
>
>> On Fri, Nov 6, 2009 at 2:27 PM, Jeremy Moles <jeremy at emperorlinux.com> wrote:
>> > On Fri, 2009-11-06 at 20:25 +0000, Kim Bale wrote:
>> >> Haha, I had a feeling you'd jump in ;)
>> >>
>> >> K.
>> >
>> > Haha, I'm sorry. :) I'm not trying to be annoying, I'm just trying to
>> > get new ideas for the ways people use stuff and what kinds of things I
>> > may be forgetting are important to people. No advertising here, just
>> > leeching infos!!!
>> >
>> >> 2009/11/6 Jeremy Moles <jeremy at emperorlinux.com>:
>> >> > On Fri, 2009-11-06 at 14:12 -0600, Nguyen Tien Dat wrote:
>> >> >> Dear all,
>> >> >> I draw a line as following:
>> >> >>
>> >> >>         osg::Geometry* geo = new osg::Geometry();
>> >> >>       // define some vertices
>> >> >>       osg::Vec3Array* v = new osg::Vec3Array;
>> >> >>       v->push_back(start);
>> >> >>       v->push_back(end);
>> >> >>
>> >> >>       // draw lines
>> >> >>       geo->setVertexArray(v);
>> >> >>
>> >> >>       geo->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINES, 0, 2, 1));
>> >> >>
>> >> >>       geode->addDrawable(geo);
>> >> >>
>> >> >> But the line is hardly to be seen because it's too thin and has white
>> >> >> color. So my question is:
>> >> >> - Can I change the color of the line? If yes, please tell me how.
>> >> >> - Can I change the thickness of the line? If yes, pleas tell me how.
>> >> >
>> >> > Out of curiosity, what are you using the line drawing for? And how
>> >> > high-quality must the lines be? :)
>> >> >
>> >> >> Thanks,
>> >> >> Dat
>> >> >> _______________________________________________
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>> >> >>
>> >> > --
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>> >> >
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>> > http://www.emperorlinux.com
>> > 1-888-651-6686
>> >
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>
> EmperorLinux, Inc.
> http://www.emperorlinux.com
> 1-888-651-6686
>
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-- 
Dat Tien Nguyen
PhD student, Computer Science Department
The University of Iowa, IA 52242
http://cs.uiowa.edu/~tinguyen


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