3D stereograms

(By Gary Beeton)

We all know that Imagine allows you to create stereo pair images for use with special 3D glasses. But did you know that Imagine 3 will, with the help of shareware, let's you create 3D images that do not require glasses and that you can also print?

I'm talking about SIRDS (Single Image Random Dot Stereograms) or sometimes called Stareogram; you know, those posters made of dots which, when you look (persistently) straight through them, will reveal extruding shapes.

It's easy! All you need: a shareware SIRDS generator (I'm not sure about the PC, but for the Amiga there's a bunch of them in Aminet under gfx/3d), Imagine 3.0 and a scene.

An example:

Load an obje ct into the Detail editor (i.e. Cow.iob). To simplify the process UnGroup any parts then Join them all together as one object.

Attributes should be: Color white, set the rest to zero (0); Bright should be on (x), set Quickdraw on (x) and Texture: ZBuffer. Now reset your perspective view and rotate your object just as you would like to see it by the camera as viewed in the perspective view. This is important because ZBuffer is relative to Global coordinates, and not relative to the camera.

Go into the "Top" view window, turn Coordinates on, move your cursor to the bottom of the bounding box and write down the Y coordinate (Y1), move the cursor to the top of the bounding box and write down the Y coordinate (Y2). These two Y coordinates should be entered in the ZBuffer texture's Y1 and Y2. Leave the color settings from white (255,255,255) to black (0,0,0) (assuming your SIRDS generator expects white as out and black as in). Save the object.

Go into Action editor, Add your object and set camera position to 0,Y1-n,0 alignment to 0,0,0 where n is the distance from the object to be viewed.

Save Changes. Go to Stage editor, add a light and place it anywhere in front of the object, turn on camera view and fine tune the placement of the camera making sure not to change it's alignment.


The resulting image should be a gray scale image which can be loaded into and processed by a SIRDS generator. I've had excellent results with this technique, many of which surpassed some commercially available SIRDS posters.

The 3-D option: X-Specs "driver"

The 3-D option in Imagine is desi gned to produce a format which is viewable using 3-D LCD shutter glasses called X-Specs. The X-Specs "driver" interleaves the top and bottom halves and syncronizes the right/left lenses with the interleave refresh rate of the display. The top and bottom halves appear squashed because each represents one field (half of the data for a full frame). Unfortunately for Imagine PC users, I think X-Specs are only available for the Amiga. This would appear to be a vestigial "feature" from Impulses' attempt to make the PC and Amiga versions have the same look and feel.

I don't think there is a way to have Imagine separate the images into separate files. To overcome this problem I would try doubling the project's vertical resolution and make the aspect ratio 2:1. Then use an image processor to reset the aspect back to 1:1 to unsquash, then separate the images. An alternate method would be to manually reposition the camera for each left and right image (this will be a big pain if you intend to animate though).

Last Update: July 13, 1995
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