[osg-users] Separate sub-graphs of the same scene

Peter Amstutz peter.amstutz at tseboston.com
Mon Mar 16 13:45:08 PDT 2009


I'm not sure I entirely understand what you're trying to accomplish, but 
perhaps you want to look into using a stencil buffer and/or pixel shader 
to control what gets rendered?

Guy wrote:
>
> Hello,
>
>  
>
>  I'm trying to merge two sub-graphs to the same image. It doesn't work 
> so well, so I'll try to explain what in general I'm trying to achieve, 
> then my not working so well solutions, and then the questions J
>
>  
>
> So, in general I want to replace an object (A) in the scene with 
> another object (B) on some condition. The object (B) is some pixels 
> which are lit up. The important thing is to keep the 3D scene distance 
> from the camera for both objects, so if the object is obscured by 
> another, then both (A) and (B) will be obscured, and if some other 
> object (C) is obscured by (A), it will still be obscured by (B). 
> Object (B) might be partially transparent.
>
>  
>
> Not working so well solution 1:
>
> Have switch for (A)/(B).
>
> The position of (A) is multiplied by view-projection matrix, the 
> result is pos'. (B) is a set of points which their vertices are pos' 
> with (x,y) replaced by the pixels I want to lit, and the new positions 
> are multiplied by the inverse-projection invers-view matrices.
>
> This solution had problems with setting the right pixels.
>
>  
>
> Not working so well solution 2:
>
> Object (B) is a set of pixel under ABSOLUTE_REF orthographic 
> projection with (x,y) of the pixels I want to lit and z is the 
> negative distance between (A) and the camera.
>
> This solution has the correct pattern of the lit pixels, but the Z 
> order doesn't seems to be correct.
>
>  
>
> The implementation of solution 2 is to add camera with ABSOLUTE_RF and 
> orthographic projection. View is identity. I set the clear mask to 0 
> since I don't want the Z-Buffer to be cleared. (opposed to huds and 
> that kind of implementations).
>
>  
>
> I used the osgviewer to put the cow at 0,0,-300 under absolute_rf, and 
> a point at 0,0,0 under separate camera with orthographic projection, 
> and the point was hidden by the cow (which is a mistake).
>
> I thought that I might need to set the zNear/zFar of both camera's to 
> be the same, but in this simple example it shouldn't matter since the 
> point Z is zero…
>
>  
>
> So first, do I have to set the zNear/zFar of both camera's to be the same?
>
>  
>
> Any ideas whats going wrong?
>
>  
>
> Other solutions for the problem?
>
>  
>
> Btw, I tried to replace the points by quads under orthographic 
> projection. The results were the same.
>
>  
>
> Thanks,
>
>  Guy.
>
>  
>
> ------------------------------------------------------------------------
>
> *מאת**:* osg-users-bounces at lists.openscenegraph.org 
> [mailto:osg-users-bounces at lists.openscenegraph.org] *בשם** *Robert Osfield
> *נשלח**:* Monday, March 16, 2009 5:39 PM
> *אל**:* osg-users at lists.openscenegraph.org
> *נושא**:* Re: [osg-users] RecordCameraPathHandler where is the 
> saved_animation.path file?
>
>  
>
> On Mon, Mar 16, 2009 at 3:28 PM, Felix Ilbring <osgforum at tevs.eu> wrote:
>
> Hi Robert
>
> I have done it. I put it to
>
> new osgViewer::RecordCameraPathHandler("C:\\ETC.path");
>
> but it was never there.
>
>
> The class has always worked for me, so can't suggest any gotcha's, 
> you'll have to open up a debug and see what the 
> ReecordCameraPathHandler is doing on your build/system.
>
> Robert.
>
> ------------------------------------------------------------------------
>
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