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Vanilla 1.1.5a is a product of Lussumo. More Information: Documentation, Community Support.

    • CommentAuthorNick
    • CommentTimeNov 21st 2008 edited
     

    Automated assistance with Tie Point picking


    This feature is one of the core tools of image orientation yet many people do not
    realise it exists. It can significantly improve the residuals of the orientation
    calculation and also speed up the workflow. To use:

    1. Assuming you have your two images of a pair open in the orientation screen, open
    the "Pick Tie Point" tool either by right clicking on an image, or from the Orientation
    menubar item.

    2. Use the zoom tool to display the same area of the left and right images where the tie
    point feature exists (remember to choose high contrast or strongly textured
    features).

    3. Accurately left click on the feature in the left image that you wish to use as the tie
    point.

    4. Enable the "auto correlation" tool to find the corresponding point via the clever
    pixel-matching algorithm by clicking the centre scroll wheel of your mouse.
    Alternatively, the auto correlator can be activated by clicking the "binocular" icon on
    the toolbar (circled below).

    5. A progress box appears which should quickly finish resulting in the control point
    being detected in the right image automatically. Note - if progress bar
    "hangs" on 70-80% for a long time, it is likely that it will not find a match so click
    cancel and try another target.


    7. If you are happy that I.M. has picked the correct feature, click "Measure" to register
    the tie point.



    ADVANCED TIP:



    The above process will work on up to FOUR images at once. This can greatly speed up
    picking tie points to link adjacent pairs of images (shown above).

    - Holding down the control button, click on the four images you wish to open e.g. left
    and right of the first pair and left and right of the next pair. Right click the mouse
    and select "open images"



    Repeat the steps 1-6 above. If successful, the tie points should be coloured YELLOW
    indicating that they are common between two stereo pairs. Note that the minimum number of
    points required to tie adjacent image pairs is 3.

    NOTES:

    - The auto correlation process only works on the visible parts of each photograph in the
    zoomed in viewport. It will not work if you have different parts of the image in the zoom
    viewport.

    - If the subject being modeled has a repeated pattern (red bricks are a classic), the
    correlator can sometimes fail by picking the wrong point, so always double check before
    clicking "measure".

    - If you have chosen good features to use as tie points (high contrast, unique etc.), the
    auto-correlation process should only take a few seconds. If it hangs on >70% for more
    than around 10 seconds it will probably fail, so click cancel and try again with another
    tie point.