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krpano Coordinate Systems Version 1.23
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Here a quick overview about the various coordinate systems in krpano.
Documentation topics:

View / Lookat Coordinate System
Ranges:
  • 360x180 degree.
  • From -180 (left) to +180 (right).
  • From -90 (top/zenith) to +90 (bottom/nadir).
  • The coordinates can wrap around and be also outside the 360x180 range, but the resulting view can be always only inside the 360x180 range.
  • 0/0 is always the center of the image.
Usages:
  • The view (viewing camera) is using the hlookat and vlookat settings to define the looking direction to the given coordinate in the panoramic image.
  • Hotspots are using ath and atv settings to the define the spherical position in the panoramic image.
  • Actions and functions might typically use h and v or x and y for addressing the spherical position.

3D Coordinate System
3D Coordinate System:
  • The 3D coordinate system is an extention of the 2D layer system (with a top-left edge) into 3D space. This is done by adding +z as a depth into the screen value.
  • This way the layer and hotspot x, y coordinates are compatible with each other.
3D Axes:
  • X-Axis: Points from left (-) to right (+)
  • Y-Axis: Points from top (-) to bottom (+)
  • Z-Axis: Points from out-of-the-screen (-) into-the-screen (+)
  • The coordinate system is left-handed.
  • Unit: 1 ^= 1 cm

Panoramic Image Arrangement
Spherical, Cylindrical, Flat Panoramic Images:
  • 0/0 is always the center of the image.
  • The images can have any horizontal and vertical field-of-view range.
Cube-face Arrangement:
  • The left cube face is at h=-90° v=0°
  • The front cube face is at h=0° v=0°
  • The right cube face is at h=+90° v=0°
  • The back cube face is at h=+180° v=0°
  • The up cube face is at h=0° v=-90°
  • The down cube face is at h=0° v=+90°
The same as Spherical / Equirectangular Image: