Hi,
Thank you for this quick answer.
I found two ways to do what I wanted :
-by adding the following line before the rendering loop (
while(!viewer->done())...):
viewer->getCamera()->attach(osg::Camera::COLOR_BUFFER, image);
So image is filled by a thread which has the graphics context current
Then the image is stored after the command viewer->frame() by using the
function osgDB::writeImageFile(...).
-by using the method setPostDrawCallback which is necessary if we want to
modify the rendered image before the storage.
Thanks a lot.
Jean-Baptiste
2008/4/1, Robert Osfield <[EMAIL PROTECTED]>:
>
> Hi Jean-Baptiste,
>
> The most likely cause of the OpenGL error is that your code that is
> calling glReadPixels doesn't have the graphics context current. You
> have to call OpenGL from the thread that has the graphics context
> current. The easist way to do his is to attach a Camera post draw
> callback, this will be called from the appropriate graphics threads.
> If you are using 2.3.x or SVN then use Camera final draw calback as
> it's called later in the draw pipeline.
>
> Robert.
>
>
> On Tue, Apr 1, 2008 at 6:47 PM, Jean-Baptiste Authesserre
> <[EMAIL PROTECTED]> wrote:
> > Hi everyone,
> >
> > I am trying to get screenshots of a generated scene with OSG. In order
> to do
> > that I am using the method readPixels of the class osg::image. But it
> seems
> > that the function glReadPixels used by readPixels fails. Here is a part
> of
> > the code:
> >
> > //start the rendering
> > float * depthBufferRaw;
> > osg::Image * depthBuffer= new osg::Image();
> > unsigned char * tmp;
> >
> > int height=1280;
> > int width=1024;
> > int i;
> > depthBufferRaw = (float *) calloc(height*width, sizeof(float));
> >
> >
> > while(!viewer->done())
> > {
> >
> > viewer->frame();
> >
> > //Get values of the color buffer
> > depthBuffer->readPixels(0,0,width,height,
> > GL_LUMINANCE,GL_UNSIGNED_BYTE);
> >
> > tmp = depthBuffer->data();
> > for (i=0; i<height*width; i++)
> > depthBufferRaw[i]=(float) tmp[i];
> >
> > //save as image
> > ...
> >
> >
> > }
> >
> > With the above code, i get an array (depthBufferRaw) with constant
> values
> > whereas i see on my screen a scene with different objects and colors.
> Thanks
> > to debug mode of VS2003, i can verify that depthBuffer->_data has been
> > allocated.
> >
> > The source code of the osg::image method readPixels is the following:
> >
> > void Image::readPixels(int x,int y,int width,int height,GLenum
> format,GLenum
> > type)
> > {
> > allocateImage(width,height,1,format,type);
> >
> > glPixelStorei(GL_PACK_ALIGNMENT,_packing);
> >
> > glReadPixels(x,y,width,height,format,type,_data);
> > }
> >
> > So, it seems that glReadPixels failed. I tried to show this by using
> > directly glReadPixels in my implementation with glGetError.
> > Strangely glGetError returns the value 1282 (GL_INVALID_OPERATION)
> > whatever the position of the call to this function in my code. And when
> i
> > tried to use this function in a loop as :
> > while (errCode != GL_NO_ERROR)
> > errCode = glGetError();
> >
> > I obtain an infinite loop.
> >
> > My questions are the following:
> > -Is that possible to use glGetError with OSG?
> > -Has anybody an idea of why the method readPixels fails in this case?
> >
> > Thanks in advance!
> >
> > Jean-Baptiste
>
> > _______________________________________________
> > osg-users mailing list
> > osg-users@lists.openscenegraph.org
> >
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
> >
> >
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