Hi Robert,
thank you for your answer.
I'll try to give some more details on the current setup:
- multiple physical displays/projectors which overlap to produce a
single (flat-)screen
- alignment and blending of the displays is done with the 3rd-party stuff
- the displays support checkerboard-stereo
In mono-mode my integration of OSG and the 3rd party stuff works
perfectly and all display do what they are supposed to do. The
post-processing is done in the camera's postDrawCallback without any
magic :) The problem starts when I enable OSGs checkerboard-stereo
because the image-distortion in the postDrawCallback will result in an
unusable checkerboard-frame. So basically I'm trying to get
checkerboard-stereo to work.
Due to the described problem, I need access to the left and right frames
to distort them individually. Normally they are "blend together" via
stenciling in osg::RenderStage::draw(). As far as I know, there is no
direct access to these frames. I could either implement some kind of
callback into OSG or implement a variant of checkerboard-stereo myself.
Currently I'm trying to render both frames individually to an FBO and
putting them together afterwards. In this case I would have control of
both frames and I would be able to manipulate them with the help of the
3rd-party code.
osg::Camera::RenderTargetImplementation::FRAME_BUFFER_OBJECT wasn't able
to do the trick since I've found no way to access the FBO OSG utilizes.
Therefore I've tried my own implementation (currently on a single
display) with the following setup and the given result in the post
before (take a look at the attached picture).
The current implementation is very similiar to the osgprerender example
(stereo is not enabled) except that I'm creating my own FBO in a
preDrawCallback of the PRE_RENDER cam. This FBO has an attached texture
and is used as the rendertarget for the first (left) (RTT-)camera.
RenderTargetImplementation for this camera has not been explicitly set.
The texture is attached to a rectangular geometry, which is itself a
child of the osgViewers camera. Unfortunately the result of the RTT
looks like the attached image. The image was saved in the
postDrawCallback. I'm pretty sure I've messed something up or missed
something. RTT with OSGs FBO works fine and I've looked at the code but
I didn't find anything.
Does someone have an idea? Or maybe another way to implement
checkerboard-stereo? It looks like some faces get culled away. If its
useful I'll post some code.
@Robert: I'm not using osgUtils low level stereo right now but I guess
some of the code would later be useful to get the correct left and right
camera-position-setup.
Nice greetings and thanks for any help or hint!
Mathias Buhr
P.S.: I was already able to do the distortion with that implementation
(with blitting the FBO-image back to the window-system provided FB to
get the 3rd party stuff working).
Am 04.08.09 19:14, schrieb Robert Osfield:
Hi Mathias,
You don't really provide enough info about your overall viewer setup
to give a direct answer. It sounds like you are using the OSG's low
level stereo support in osgUtil and combining this with a 3rd party
code that does distortion correction or similar. Doing low level
stereo and distortion correction is really going to work visually even
if you got it to work code wise, as the low level stereo support in
osgUtil assumes a flat display.
Have a bash at explaining what your system is trying to do at a high
level and then others will have a better chance of suggesting how to
go about it.
Robert.
On Tue, Aug 4, 2009 at 4:10 PM, Mathias Buhr<[email protected]> wrote:
Hi,
before going into the details of the problem, I'd like to explain what I'm
trying to do and what I have done until now.
I have a 3rd-party function/method which is out of my scope. It seems to
read and write the window-system provided framebuffer and
manipulates/distorts the image. The first implementation was through calling
this function in a postdraw-callback. Everything works fine this way.
Unfortunately this is not possible if the CHECKBOARD flag is set because the
postdraw-callback is called after the complete frame (including the
stenceling for the checkerboard) is rendered. The function would distort the
checkerboard. Hence, I have to apply this function for each "eye"
separately.
This seems possible with some changes to OSG itself but it also would break
the possibilty to upgrade later. So I decided to take another approach:
I've tried rendering to an FBO (RTT, similar to osgprerender) but I can't
apply the function anymore in the postdraw-callback (gives GL errors). Since
there is no access to the OSG-managed FBO (for bliting from FBO to FB) I
have implemented my own and rendered to that instead. I'll give you a brief
overview for that:
MainCamera
- addChild(QUAD_STRIP) //an osg:Geode with an
osg::Texture2D
- addChild(LeftCamera)
- PreDrawCallback:
- if (!fbo) glGenFramebufferEXT
- glBindFramebufferEXT
- glFramebufferTexture2DEXT //attach the osg::Texture2D
- PostDrawCallback:
- glBindFramebufferEXT(0) //bind window-system fb
LeftCamera is set to PRE_RENDER
This approach gives me the result which is shown in this picture:
http://www.apparatus.de/test1.png
Does someone have an idea what is going wrong or what I've missed? I've
looked at the RenderStage code (and much more :-) ) but I haven't found
something that might be the problem.
Or maybe there is another (better) approach to this problem. Any hints for
that?
I would appreciate any help! Thank you very much for reading :-)
Greetings
Mathias
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