Create Popup Anaglyph

Popup Anaglyph Samples

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' (often called phantograms) consist of a pair of carefully-executed images, taken with the camera pointing-down, normally at 45 degrees, to the subject.
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 it's back.
When viewed at the correct angle 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.
('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 exactly 45 degrees, is pointed at the exact 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.
One possible method is given in this NSA 2004 Tutorial.
(you have to temporarily enable JavaScript for that site).
Some people claim that camera separation should be the same as eye-spacing and not the 1/30 rule.
You may wish to check this.
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.
For the following description of the workflow, download image phtg0152 .
Load the pair of images and select 'Adjust/Create Popup Anaglyph'.

Correct simple rotation errors

This procedure must be carried-out before any perpective rotations.

Display both images at 100% and drag with mouse until the left edge of the red image is at the left of the screen and you can see your bottom, horizontal guide-line (or bottom edge of the carefully aligned background paper).

Display just the red image and draw a line with the mouse (left-button down) along that edge as far to the right as possible.
On large images you may not be able to mark the entire bottom edge but that should have no effect on the final result.
Display both images again and drag so the left edge of the cyan image is at left of the screen.

Display just the cyan image and draw a line with the mouse along that edge as far to the right as possible.
Click 'Auto Adjust' and both images will be tilted the required amount to make the bottom edges horizontal.
Click '100%' to return image to window-size.
Finally, ensuring that 'Reverse Perspective Rotation' is not checked, click 'Popup Anaglyph' tab and 'Start(Set to 45 degree)' to apply a 45 degree default, perspective-rotation about the horizontal axis and an increased canvas-height of 5 units.

Perspective Correction

If the image is cut-off at the top, anytime the perspective-rotation around the horizontal axis is non-zero, you may alter the 'canvas' height by clicking the 'canvas height +' numeric Up/Down CheckBox.

Select red image only and adjust 'focal length' until the side guidelines are parallel to each but probably tilted.
In other words they form a parallelogram.
Turning on the grid overlay will aid this process and you may alter the number of grid-divisions by using the numeric Up/Down CheckBox to the right of the 'grid' checkbox.

Now adjust the red-channel 'shift' value until the tilting lines become as vertical as possible.
If necessary, small changes may be made to the nominal 45 degree perspective rotation around a horizontal axis, in order to get the lines as vertical and parallel as possible.
Repeat these operations with the cyan channel.

Equalise Image Sizes

With both images displayed, use the horizontal slider to superimpose both images and using the vertical-slider, align the bottom of the images.
Turn on the grid and check image height.
If the cyan image appears smaller (as shown above), the left channel needs making larger.
(remember, when both images are displayed, the left channel is displayed with a cyan color).

Increase image magnification until heights are same after the bases are aligned.
That is shown in the above image.

Set the Stereo Window
Using the horizontal slider, shift the images until the vertical lines at each edge are superimposed.
If you are using the grid mentioned above, the target circles should also be aligned.
There should not be color-fringing at either edge.
The window should now be correctly set and you may check with your red/cyan glasses and sitting-back a little(after turning-off the grid).

Save Adjustment Settings
You may save the current adjustment settings by clicking 'Save'.
The settings are saved in the registry (overwriting the current contents) and also in a file "easy_set.txt" located in the same folder as SPM.
You may load the current values from the registry by clicking 'Restore' or from "easy_set.txt" by clicking 'Restore(File)' .
The data format is as follows :-

[Data]
Easy Adjustment=Rotation_l,Rotation_R,Zoom_L,Zoom_R,Alignment_x,Alignment_y,V_Perspective_L,V_Perspective_R, H_Perspective_L,H_Perspective_R,Focal length,Shift_L,Shift_R,Image Height+,

If you do not wish certain values to be over-written, replace their entries in the file with an '*' .
e.g. Easy Adjustment=*,*,Zoom_L,Zoom_R,Alignment_x,Alignment_y,V_Perspective_L,V_Perspective_R, H_Perspective_L,H_Perspective_R,Focal length,Shift_L,Shift_R,Image Height+,

In the above, the current simple-rotation values for the left/right images would not be over-written.

Press 'OK' to complete the process.
If the SPM folder contains a file named 'wall.gif', 'wall.png' or 'wall.jpg', the black background will be replaced by that texture.
A popup anaglyph object movie may be made by placing the subject on a turntable (such as an inexpensive 'Lazy Susan') and typically taking 36 images at 10 degree intervals.
Move the camera laterally and repeat.
Use the first image-pair to determine the adjustment parameters and then save them and use to manually-process the entire batch of images.
An example movie is available for download and is most conveniently viewed on a flat-screen display.

Crop and Save Image

Crop the image to exclude the calibration marks and save as separate left/right pair in an uncompressed format such as PNG.
Even if you just want anaglyphs, it is best to save your work as uncompressed non-anaglyph images.
These may then be used with other features in SPM (such as described below).
Change stereo viewing-mode to Anaglyph (half-color if desired) and print-out.

Place the print on an evenly-illuminated flat surface and viewing from 45 degrees adjust your distance until the 'sweet spot' is found.
Enjoy your first Popup Anaglyph !

....
Images by kind permission of Steve Boddy ©

Batch Creation of Popup Anaglyphs

If you have a batch of images taken under the same setup conditions, including object-movies, rather than saving the first image, select the Multi Conversion option.
Remember to restore the adjustment settings from your saved text file, select the required output-format and some or all images in your folder.
Click 'OK' and all the Popup Anaglyphs will be automatically created.

Batch creation of Camera-view of Anaglyphs

For use with a website gallery of Popup Anaglyphs, it is useful to display a stereo image of what a viewer looking at the completed anaglyph would see.
There is no need to take a photo of this, simply load the adjusted 'Popup Anaglyph' left/right images into SPM, choose 'Create Popup Anaglyph' and check 'Reverse Perspective Rotation'.
Click 'Start(Set to 45 degree)' to apply a 45 degree default, perspective-rotation about the horizontal axis and an increased canvas-width of 5 units.
Make any minor adjustments for the required effect and save the settings as a suitably-named text-file.
Click 'OK' and select the Multi Conversion option.
Remember to restore the adjustment settings from your saved text file, select the required output format and some or all images in your folder.
Click 'OK' and all the Camera-views of your Popup Anaglyphs will be automatically created.

....

(to be viewed with anaglyph glasses)

Images by kind permission of Steve Boddy ©