Hi Doug, How exactly is this library drawing the video? Is it feeding the video data into a texture, and applying that texture onto a simple quad? If so, it seems like the best approach would be to use the osg::TexMat class to transform the texture coordinates of the quad to simulate a zooming in effect. Either way, it's difficult to say what is going wrong without knowing more about how this library works.
Cheers, Farshid On Thu, Mar 15, 2012 at 1:01 PM, Doug Domke <doug.do...@boeing.com> wrote: > Hi, > > We have an OSG-based application that uses a 3rd party library to draw > video. We want my application to perform a "digital zoom" on this video. > Given the API to this library, we wrote an OSG node with a draw callback > that calculates the viewport for the video to draw in, and lets the library > do its magic. > > My theory for the "digital zoom" feature is to give the library a larger > viewport (it always draws the same scene into the viewport) and > cull/clip/stencil the result. My current attempt is in using a glStencil > in the draw callback as follows: > > > Code: > glEnable(GL_STENCIL_TEST); > glClear(GL_STENCIL_BUFFER_BIT); > glStencilFunc(GL_ALWAYS, 1, 1); > glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); > glBegin(GL_QUADS); > glVertex2d(left, bottom); > glVertex2d(left, top); > glVertex2d(right, top); > glVertex2d(right, bottom); > glEnd(); > glStencilFunc(GL_EQUAL, 1, 1); > <draw video> > glDisable(GL_STENCIL_TEST); > > > > Unfortunately, the video ends up disappearing entirely. If I remove the > Code: > glEnable(GL_STENCIL_TEST); > > line, the video draws in the larger viewport and overlaps areas that it > shouldn't. > > Can anyone identify a flaw in my code? Is there another approach that may > be better? > > Thank you! > -Doug[/code] > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=46318#46318 > > > > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org >
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