Is there a place in the hugin documentation that explains the axes and directions hugin uses?
Both as a user and as a developer, this is a topic I have repeatedly needed, looked for, failed to find, experimented and learned, and then forgotten. Until I recently finally took notes. I primarily care about the six parameters of the camera's point of view: Yaw, Pitch, Roll, TiX, TiY, and TiZ. But other parameters likely also clearer definition of direction. I think of those as all describing both the motion of the camera in moving it from a hypothetical centered position to its actual position* and* the motion of individual pixels as they are moved from their positions in an input image to their positions in the output image (those two are the same direction of motion). The opposite direction (from output position to input position) is an equally valid set of definitions, but I like those less. As best as I can tell by experimenting: Hugin's X axis points right Hugin's Y axis points down Hugin's Z axis points back (positive values behind the observer) Hugin's Yaw is a positive rotation "on" the Y axis Hugin's Pitch is a positive rotation "on" the X axis Hugin's Roll is a positive rotation "on" the Z axis I am using the right hand rule for "positive" agreeing with every online site I have read on this topic: On your right hand, point your thumb in the direction an axis points (direction of higher values of that coordinate); curve your fingers so they indicate a direction circularly around the direction your thumb points; that is the positive rotation direction. There is no similar agreement on whether that is clockwise or counter-clockwise: Most sites think positive is counter-clockwise as most assume (and few state) that the axis is pointed *at* the viewer who sees counter-clockwise (as your thumb would if you point that right-hand-rule axis at yourself and see your fingers curved counter-clockwise). Fewer, but still quite a large number see that as clockwise because they have the viewer looking in the same direction that the axis points. Most online sites defining Yaw, Pitch and Roll, say those are on the Z, Y and X axes respectively, making hugin's choice of Y, X and Z important to document (unless I somehow got this wrong). Hugin's choice of rightward, downward and backward for X,Y,Z is also unusual, but there doesn't see to be any "usual". I expect we all learned rightward, forward and upward in basic math classes, but serious online discussions don't typically follow any standard other than right hand. All the sites (and apparently hugin as well) agree that the sequence is Yaw then Pitch then Roll for "intrinsic" rotation which is mathematically the same as "extrinsic" rotation in the sequence Roll, then Pitch, then Yaw. Intrinsic rotation is what I think of for camera motion: 1) Rotate on Y 2) Rotate on X' (where X' is the camera's X axis after its rotation on Z) 3) Rotate on Z'' (where Z'' is the camera's Z axis after both its earlier rotations) Extrinsic rotation is what I think of as the motion of a pixel from input to output: 1) Rotate on the global Z axis 2) Rotate on the global X axis 3) Rotate on the global Y axis I would appreciate: A: Pointer to where this was already all documented and I wasted your time re-documenting it (but the exercise helped me cement it in my mind to help my future use and enhancement of hugin++) B: Corrections. What did I get backwards or seriously wrong? C: Comments. Such as are there simpler ways to be precise about these things. D: Similar info on parameters other than these six. -- A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ --- You received this message because you are subscribed to the Google Groups "hugin and other free panoramic software" group. To unsubscribe from this group and stop receiving emails from it, send an email to hugin-ptx+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/hugin-ptx/44ba8ca3-d1f0-4d49-81d1-549b95938da6n%40googlegroups.com.
