Axis angle rotations and changing rotation values

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Discussion Overview

The discussion revolves around the issue of inconsistent rotation values for a 3D object (a cube) when transferred between two applications. Participants explore the implications of axis-angle representation and the potential reasons for the discrepancies in rotation values while keeping translation and scale values constant.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the rotation values change when transferring a cube between two applications, despite unchanged translation and scale values.
  • Another participant emphasizes the need to clarify whether the applications are custom-built or third-party, and whether the documentation has been consulted.
  • Questions are raised about how the applications represent composite bodies and the nature of the transfer process (atomic action vs. detachment and attachment).
  • A participant points out that the angles provided may not independently represent a rotation, suggesting a relationship between the angles and the axis of rotation, and questions how the angle of rotation is defined in this context.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the reasons for the rotation value discrepancies, and there is no consensus on the underlying cause or solution. Multiple viewpoints and questions remain unresolved.

Contextual Notes

Participants note the lack of clarity due to the closed-source nature of the applications and the absence of documentation on how data is stored and represented.

dumb_squared
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I have two 3d applications and when an object(a cube for example) is transferred between them, the rotation values of the cube change(the object stay at the same location. translation and scale values stay the same) and I can't find why that occurs and it's driving me crazy.

app 1 rotation values:

x:-27,077
y:-25,026
z:15,933

Axis-angle representation of the above

-0.7096853 0.4914011 -0.5048483 -42.20802

app 2 rotation values:

x:33.8493041
y:-13.7234678
z:26.2455062

I've read a few wikipedia articles on rotation and specifically axis-rotation stuff but I haven't really figured out what's really happening.

Any help is appreciated.
 
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You're jumping in a bit to deep, getting to specifics way too early. Before we get to the specifics, there are some key important question that needs to be addressed:
  • Are these your applications or are the someone else's? In other words, did you write the code?
  • If you didn't write the code, did you carefully read the documentation (if it exists) and follow it?
  • If you did write the code, did you carefully test it?
  • How does the code represent composite bodies, sub-bodies, and the connections between them?
  • Is this transfer is an atomic action, or is it essentially a detachment immediately followed by an attachment? If it's the latter, is it the attachment or detachment where things go awry?
 
D H said:
You're jumping in a bit to deep, getting to specifics way too early. Before we get to the specifics, there are some key important question that needs to be addressed:
  • Are these your applications or are the someone else's? In other words, did you write the code?
  • If you didn't write the code, did you carefully read the documentation (if it exists) and follow it?
  • If you did write the code, did you carefully test it?
  • How does the code represent composite bodies, sub-bodies, and the connections between them?
  • Is this transfer is an atomic action, or is it essentially a detachment immediately followed by an attachment? If it's the latter, is it the attachment or detachment where things go awry?

Sorry about lack of clarity. Both applications are closed sourced and there is no information about how they store the data.

The transfer file format converts x,y,z angles to Axis-angle representation
 
Yes, but what do those angles have to do with a rotation? A single axis of rotation can be given by its three direction angles- the angles the axis makes with the three coordinate axes. Also, if this is the case, x, y, and z are not independent. We must have [itex]x^2+ y^2+ z^2= 1[/itex]. Is that what you mean? Where do you give the angle through which you are rotating?
 

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