Creating a cylindrical QTVR source image from a camera of any focal length in StudioPro or Strata3D/pro

Setting Up The Panoramic Camera
Before you can create a QTVR panorama, you need to create a source image for it. Insert a camera object into your model. Select "Panorama" in the Type field of the Object Properties palette (Fig 1). Set the Ratio field to "1.00:1". This will create a square camera window. It will also avoid image distortion and allow you to see the lens coverage of your camera during the setup stage. To avoid accidentally altering the camera window's aspect ratio, depress the lock button at the top of the camera window (Fig 2).

The Constrain Roll checkbox should be checked so that your camera does not roll during manipulation. Next, ensure that the camera is perfectly horizontal. Open the Project window and check that the camera's Base Properties:Tracking parameter y=0 (Fig 3). The x and z parameters can be any value. However, for the sake of consistency when creating more than one panorama within the same model, it is often best to have the camera pointing either in the direction of the x axis or the z axis.
Fig 1
Fig 1
Setting The Camera View Angle
The camera's view angle, or field-of-view (fov) depends on the focal length of the lens chosen. This can be set with the slider at the top of the camera window. However, for precision, it is best to enter a value in the View angle field in the Object tab of the Object Properties palette (Fig 1). View angles narrower than 40 degrees or wider than 120 degrees are seldom used in creating QTVR panoramas.
Fig 2
Fig 2
Note that the default panorama camera settings in StudioPro or Strata3D is for a camera lens of 15-17mm focal length. If this is not suitable for your scene, feel free to use any lens with a different fov instead. However, there are certain caveats about choosing a fov, as described in the Tips section below.

Calculating The Image Size To Render For Any Lens
The QTVR panorama you create is basically a 2-dimensional image wrapped around a virtual cylinder (Fig 4). The circumference of this cylinder (c) is the width of the image, while the height of the cylinder (h) corresponds to the image's height.

Decide on one of the image's dimensions beforehand. (I usually decide on the width. See Tip #1 below.) Then use the following equation to calculate the other dimension:
Fig 3
        c = (pi) x h / tan (0.5fov)

c = the width of the panoramic image, i.e. the circumference of the virtual cylinder
h = the short dimension, or height, of the panoramic image
fov = field-of-view, or the lens' view angle in degrees
pi = 3.141592654...
r = radius of the circle which defines the width of the cylinder (r is not required in the calculation)

For example, suppose you use a 35mm lens (63 degrees fov), and set the height of the panoramic image at 580 pixels. Then, using the equation above, the width of the image will work out to be 2973 pixels initially. However...

Your panoramic image will be "diced" by whichever application you use to create the final QTVR panorama. (Creation of a QTVR panorama is currently not handled by StudioPro or Strata3D.) It is a condition of the dicing process that both dimensions of your image are evenly divisible by 4, and the long dimension (width) is also evenly divisible by the dicing factor (usually 24). The closest number to 2973 which satisfies both these conditions is 2976. Thus, your calculated panoramic image's final dimensions will be 2976 x 580 pixels.

Rendering
The image dimensions you have calculated above will be entered into the image Size fields in StudioPro's Render dialog (Fig 5). Deselect the Constrain proportions checkbox before you render. Avoid ticking the Anti-alias filter checkbox in the Render dialog, as Apple's QTVR engine will automatically anti-alias your QTVR panorama when you run it. You don't want TOO much anti-aliasing.

Fig 3
Fig 4
Fig 4
Fig 5
Fig 5
If you do not have an application to create your QTVR panorama, you can get Apple's limited MakePanorama2 tool. Unfortunately, this tool has no Windows version at the time of writing this tutorial. Before you use this tool, you will need to rotate your rendered image 90 degrees counterclockwise in a graphics editor (e.g. Adobe Photoshop).

Tips
1) When you first open a QTVR panorama, you are presented with a window. You interact with this window to pan, tilt and zoom the panorama. This window has a default view angle (or fov), just like any other virtual camera. If you notice a "wide-angle warping" effect when you are panning the panorama (especially when you have zoomed out in the QTVR window), then the window's view angle has been set too large. (Some applications permit you to set the default view angle during the QTVR creation process.) Not surprisingly, an ideal view angle is that which corresponds to a "normal" 50/55mm lens, about 46 degrees.

Once you have decided to use a view angle of 46 degrees for the QTVR window, you will need to work out what is the height of the panoramic image which will encompass this view angle. To do this, you need to decide on a vertical dimension for the default QTVR window. Then, using this as an h value and a fov of 46 degrees, work out the circumference, c, of the corresponding cylinder. This c value, together with the fov of the camera in your model, is then used to calculate the height of the panoramic image which will be generated.

Conversely, once you have created a source image for a panorama, you may want to work out the dimensions of the ideal QTVR window for viewing this panorama by using the equation above with a 46-degree view angle in mind.

In general, experiment with your default QTVR window's view angle until you are satisfied with the amount of distortion you see during panning.

2) The best compression codec to use when dicing a source image is Photo-JPEG (in my humble opinion). Some people prefer the Sorenson compression codec, while others are satisfied with cinepak compression. Try whichever works for you. This assumes, of course, that you have control over the dicing process and the QTVR panorama's creation.

3) If your QTVR panorama creation tool allows it, set the panorama de-warping quality to partial instead of full. This setting is saved only if you are making QTVR2 panoramas. This improves panning performance.

Related Topic
How to create a cubic QTVR panorama.

© Swee Oon
DreamReality
The author acknowledges the assistance of Jonathan E. Langer in the preparation of this tutorial.