Create Popup Anaglyph

Please note that in order to reduce download-size, the same dialog-box has been used when describing various operations.
The values displayed are not representative of any particular operation.

'Popup Anaglyphs' are technically 'oblique anamorphs' and consist of a pair of carefully-executed images, taken with the camera pointing-down to the subject.
Any angle between 15 and 75 degrees may be used but 45 degrees is the norm.
A standard lens approximates the angle-of-view of the eye but a wide-angle lens may also be used and the result will be geometrically-correct.
Anaglyph display is the normal mode for amateur use but they may also be lenticular, projected or holographic images.
The camera may be a real camera used with real subjects or a 'virtual camera' used with a scene rendered with a 3D modelling program such as Bryce.
The perspective distortions, due to the camera-tilt and offset, are corrected by SPM and an anaglyph print is made or the images may be viewed on a monitor laid flat on its back.
When viewed at the correct angle, height and distance, the subject appears to popup from the surface in such a realistic manner that you can place a ruler alongside and take measurements.

There is only a single very precise 'sweet point' for that accuracy of illusion.

For geometrically-correct results the camera spacing is related to the virtual size of the subject in this way :-
Camera spacing/eye spacing = Subject real size/ Subject virtual size.

So, for a virtual image 1/10th of actual subject size, camera-spacing would be 600 to 700 mm.
Viewing distance should then be 1/10th taking-distance.

Another way of deriving camera-spacing is to consider taking-height of the subject and subsequent viewing height of the image.
You may define your own values, but let us assume your eyes are 500mm above print when sitting, 800mm above when standing and 1600mm when standing and the print is on the floor.
Average eye-spacing is approximately 1/8, 1/12 and 1/25th of those heights so (by similar triangles) your camera-spacing should be those same fractions of camera height above the ground, an easily measured value.
Three separate image-pairs at those spacings will cover the vast majority of viewing situations.
If you attempt to use a normal stereo-camera separation for such a large subject viewed at such a small size, you will be able to achieve the popup effect but the subject will be cardboard-like, lacking depth (as in popup books).
This may or may not be desirable.
The important thing is to accurately align the ground plane to the monitor window and then perform any 'tweaks' to the image.
Try to create realistic lighting, shadows, etc to aid the realism of the illusion and a light textured background to minimise ghosting.

('Popout Anaglyphs' may be viewed on a normally-oriented monitor at 45 degrees from the side. SPM does not support creation of these).
In principle, they are very simple to make and you may spend minutes or hours on the initial setup.
You simply ensure the unshifted camera is level but tilted-down and is pointed at the centre of the subject and the camera and slidebar are exactly parallel to the horizontal guidelines of your grid.
The highest quality, most accurate results require care and attention to detail and there are various working methods.
Ensure the camera is parallel to the subject or the image-plane will appear tilted towards one of the corners. One possible method is given in this NSA 2004 Tutorial.
Calibration marks and horizontal and vertical guidelines should be present on the image, but the background behind the subject can be plain card of a carefully-chosen color to minimise ghosts.
A suitable calibration-grid may be downloaded in ZIP format.
With a certain amount of work, the plain background can be replaced with a texture-image of your choice.
Until you have more experience, it is best to avoid subjects that are too tall.
For beginners, SPM allows the errors in less-than-perfect source-images to be corrected and pleasing results obtained.
You should ensure that there is sufficient 'empty' space around your subject, otherwise the sides may be cut-off when applying the perspective-rotation.
SPM undoes the distortions caused by perspective, camera tilt and offset by using the controls specified in the animation below.
Each frame shows the image before applying the indicated adjustment:-

The distorted background rectangle is converted to a parallelogram, then a foreshortened rectangle and finally a correctly-proportioned rectangle.

For the following description of the workflow, download image phtg0152 .
Load the pair of images and select 'Adjust/Create Popup Anaglyph'.