[osg-users] Using OsgSim Overlay

Vaibhav Bansal vaibhav at darshan3d.com
Fri Nov 20 23:23:10 PST 2009


Thanks Glenn for the tip J

 

Best Regards

Vaibhav Bansal

 

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Glenn
Waldron
Sent: Saturday, November 21, 2009 12:20 AM
To: OpenSceneGraph Users
Subject: Re: [osg-users] Using OsgSim Overlay

 

Vaibhav,

 

You may also want to investigate the shapefile_stencil.earth example (which
uses the model_feature_stencil plugin). This uses a stencil buffer technique
to drape vector data on the terrain. Make sure you get the absolute latest
SVN though. For lines, you'll need to build in the GEOS support as well (use
geos 3.1.1 on windows) to get geometry buffering.

 


Glenn Waldron : Pelican Mapping : http://pelicanmapping.com :
+1.703.652.4791



On Fri, Nov 20, 2009 at 1:53 AM, Vaibhav Bansal <vaibhav at darshan3d.com>
wrote:

Hello Glenn,

 

Thanks for your help.

 

I was working on osgearth1.2 till now, however on your advice I updated to
latest svn.

I ran shapefile_overlay.earth provided with osgearth tests on osgviewer.

However it seems that the artifacts were still reproducible L at certain
viewing angles.

(It was not there just for a fration for texture update but persisted at
that viewing angle)

 

Attached ScreenShots.

 

It seems that I will have to look into the code of overlay node.

 

Regards

Vaibhav Bansal

 

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Glenn
Waldron
Sent: Thursday, November 19, 2009 9:31 PM


To: OpenSceneGraph Users
Subject: Re: [osg-users] Using OsgSim Overlay

 

I'm no shader expert, so I cannot answer that.

I do know that osgEarth plays well with OverlayNode though -- it has some
built-in vector overlay support that uses OverlayNode in perspective mode
(see the osgearth_feature_overlay driver).


Glenn Waldron : Pelican Mapping : http://pelicanmapping.com :
+1.703.652.4791

On Thu, Nov 19, 2009 at 10:24 AM, Vaibhav Bansal <vaibhav at darshan3d.com>
wrote:

Hello Glenn,

 

The view dependent-with-perspective-overlay uses a shader, I am already
using a shader for my terrain(base geometry, osgearth).

Secondly for VIEW_DEPENDENT_WITH_ORTHOGRAPHIC mode the projected texture
resolution does not decrease(/projected area does not increase) even when
the viewing direction is near parallel to terrain, it stretches 'only' at
certain specific angles.

 

Is there a way to use overlay if I am already using a shader on my base
terrain?

 

Thanks and Regards

Vaibhav Bansal

 

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Glenn
Waldron
Sent: Thursday, November 19, 2009 6:52 PM


To: OpenSceneGraph Users
Subject: Re: [osg-users] Using OsgSim Overlay

 

Vaibhav,

The area covered by the projected texture changes based on your view angle.
As your angle of view gets less steep, the texture resolution appears to
descrease since it has to cover a larger area. Try
view-dependend-with-perspective-overlay, which helps with this issue. Also,
increase the texture size hint in the OverlayNode api.


Glenn Waldron : Pelican Mapping : http://pelicanmapping.com :
+1.703.652.4791

On Thu, Nov 19, 2009 at 7:29 AM, Vaibhav Bansal <vaibhav at darshan3d.com>
wrote:

Yes, this is what the overlay node does for me.
But I am unable to understand, why the stretching occurs only 'at' some
specific angles.


Regards
Vaibhav Bansal

-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of J.P.
Delport

Sent: Thursday, November 19, 2009 3:47 PM
To: OpenSceneGraph Users
Subject: Re: [osg-users] Using OsgSim Overlay

Hi,

Vaibhav Bansal wrote:
> Hello jp,
>
> Thanks for the quick reply.
> How do I check if the 'resolution' of ovelay geometry is changing.

imagine the following:
You want to overlay a 1024x1024 checkerboard onto the earth and you have
a 512x512 overlay texture. If you view the whole earth it obviously
would not look good - too much detail to fit into the texture. What the
view dependent modes try to do is this: When you zoom in, you only see a
piece of the checkerboard, so now the 512x512 texture can contain only a
piece of the checkerboard and so you see "more detail" of the overlayed
geometry.

I think this is the effect you are seeing when you are moving the view
around.

jp

>
> Regards
> Vaibhav Bansal
>
> -----Original Message-----
> From: osg-users-bounces at lists.openscenegraph.org
> [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of J.P.
> Delport
> Sent: Thursday, November 19, 2009 2:41 PM
> To: OpenSceneGraph Users
> Subject: Re: [osg-users] Using OsgSim Overlay
>
> Hi Vaibhav,
>
> Vaibhav Bansal wrote:
>> Hello,
>>
>> I have added a geometry as an overlay over another geometry.
>> The overlay texture seems to distort(stretch) under certain viewing
> angles.
>> It seems the projected texture is generating incorrect texture
> coordinates.
>
> The texture coordinates might be OK, but the resolution of your
> overlayed geometry might change in the generated overlayed texture. What
> happens in OBJECT_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY? Does the
> resolution/stretch stay the same?
>
> jp
>
>> The white area is the overlaySubgraph geometry, and the colored area is
> the
>> Overlay Node (base) geometry.
>> The overlay mode is VIEW_DEPENDENT_WITH_ORTHOGRAPHIC_PROJECTION.
>>
>> Can anyone suggest where should I start troubleshooting.
>>
>> Thanks
>> Vaibhav Bansal
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> osg-users mailing list
>> osg-users at lists.openscenegraph.org
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>

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