XML files VS simple mode
The SPi-V engine is capable of showing tours of multiple panoramic scenes, with quite a number of features ranging from simple hotspots to animated elements, adaptive dynamic range, etc. These features are configured using XML files.
XML files are quite similar to HTML files, so if you have ever hand-edited a HTML files to make a webpage, learning the XML format for the SPi-V engine should not pose much of a problem. Nowadays, most people use WYSIWYG editors to edit HTML documents. It is likely that one day there will be WYSIWYG editors that will let you edit SPi-V XML files. Until that time, you will have to create and edit the XML file by hand, in a text editor.
For simply displaying a panoramic image, writing a complex looking XML file might be overkill though. For certain panoramic formats, you can use SPi-V's simple mode.
Opening a fileThe mode SPi-V operates in is determined by the file you open (for information about how to open a certain file in the SPi-V engine, read this how to article). If you open a valid SPi-V XML file (.xml or .spv), all SPi-V features will be available and you can configure just about anything in the viewing experience.
If on the other hand, you're pointing the SPi-V engine directly at an image file, SPi-V will try to see if it can guess how to display the image you referenced purely by looking at the image dimensions. This saves you from having to write an XML files, but you're missing out on most of the configuration options.
SPi-V applies the following rules for guessing the panoramic projection:
- For images where width = 6 * height or height = 6 * width, SPi-V assumes a cubic projection: 6 cubic faces, collected into either a horizontal or vertical strip. The order of these images is 'front', 'right', 'back', 'left', 'top', 'bottom'.
- For images where width = 2 * height, SPi-V assumes a spherical projection, also known as equirectangular or psphere. The image is assumed to have a field of view of 360 degrees horizontally and 180 degrees vertically.
- For images where width > 2 * height, SPi-V assumes a cylindrical projection. The images is assumed to have a horizontal field of view of 360 degrees, the vertical field of view is automatically calculated.
- Other images are not as easily recognisable, and are assumed to be flat images, with a horizontal field of view of 10 degrees. The small field of view of these images will minimise perspective distortion when 'looking around' in the image.