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Thread: Precise Screen and Video Capture

  1. #1
    Junior Member Newbie
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    Precise Screen and Video Capture

    I'm trying to write a program that will be capable of tracing any pixel back to the original object coordinates. (If there is a program/library/etc. that does this already please shut me up now and I'll stop reinventing the wheel ) However the pixel coordinates need to come from a saved rendering (in a bitmap or any format that is easy to save to) and the few ways I've seen to save a rendering do not discuss whether they are accurate to the original screen.

    Also, I need to extend this later into recording multiple frames (perferably video) that are also precise. I know recording is possible (Quake III) but I do not know how feasible it is.

    This all has to be very precise because it will act as ground truth data for image processing algorithms.

    Thanks,
    Colby

  2. #2
    Super Moderator OpenGL Guru imported_dorbie's Avatar
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    Re: Precise Screen and Video Capture

    It can be done accurately if you know the viewing parameters. Things like the original frustum and camera position. A lot of the difficult work is in figuring out those things if you don't have them.

    There is a lot of published research on this kind of thing.

  3. #3
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    Re: Precise Screen and Video Capture

    My main concern is 1) how should I output the rendering for best results and 2) do I merely need to adjust the viewport transformation to get accurate correlations between the pixel coordinates and the object coordinates (given that I know all the stages between the viewport transformation and object coordinates).

    Thanks,
    Colby

  4. #4
    Super Moderator OpenGL Guru imported_dorbie's Avatar
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    Re: Precise Screen and Video Capture

    Yes, you have all you need. OpenGL even defines the exact pixel mapping w.r.t. viewport edges in the spec.

    Make a glReadPixels call and write with your non lossy format of choice.

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