Stereo Renders

Stereo Miniatures

Viewing the world through a window is not always what we would like to achieve with our stereo images. Most of the time we would like to produce an image that would look like if it was grabbable from the screen. Other times, we would like to reproduce the image onto a poster. They require different setups than the basic one.

Deriving parameters for miniatures

It may, sometimes, be desirable to reproduce the image of a model representing a real size character but as if it was a miniature located at the same distance as the computer screen. It is then possible to have part of the character stick out of the screen. I call these images miniatures because to achieve this in such a way that the scene will still look round and solid, it is necessary to consider the scene as if it was a miniature of the real scene and scale all the stereo viewing parameters accordingly.

For instance, lets say that the model we want to display is a real size person but we would like it to be viewed as if it was at the screen's distance and still view it in a medium shot. Normally, as we have seen in "Stereo for real", to render the model in medium shot, we would need to place the model at 600cm distance from the camera and place the viewing plane at 60cm from the camera which is the distance from which we want to view the picture on the computer screen.

To achieve the planned image, the viewing plane must be placed where the model is located which is 600cm. If the image is still to be viewed at 60cm distance, this means that we moved everything by a factor of 600cm / 60cm = 10. Likewise, it will be necessary to set the Eye distance to 6.5cm × 10 = 65cm. This factor of 10, in this case, is equivalent to scaling everything down by a factor of 10. The focal length stays unchanged.

So the formula to find the eye distance from the position of the viewing plane is :

EyeDistance = 6.5cm × ViewingPlaneDistance / ViewerDistanceToScreen.

Modifying only one of the two parameters alone will not produce the desired result.

Results

Click on any image to open a larger PNG image with better channels separation.

This is the result of the above operation. Observe that the image now appears just behind the screen and that the scene still have retain its proper depth.

This is the image obtained when lengthening the Viewing Plane Distance only. Note how the scene appears flat even though it now appears to be just behind the screen.

This image have been obtained by multiplying the Eye distance by a larger factor then 10. The result is a scene that feels much more elongated in depth than normal.