Rotation representation in XML

[lukas]

I have a question about rotation representation. In the program, there's three parameters representing the rotation (X,Y and Z), but when I save a simulation and export objects.xml, I see there's four parameters in the <rot> element, separated by semicolons. I am familiar with Euler angles, but I've heard there's several types of rotation representation, some with three and some with four parameters. Which representations do Universe Sandbox use?

[Dan Dixon]

The file format saves using the normalized rotation axis (x,y,z) and the angle of rotation along that axis:

So a value of: 1,0,0,90 - would be an object who's axis was perfectly aligned with the x axis and then rotated 90 degrees along that axis.

Does that help?

[Uskfver]

I have not used Universe Sandbox but I found this forum while searching Google for my current issue, which I believe is represented in the same format.

How is this rotation representation used for rotation on multiple axes? For example, if I want to rotate 90 degrees around the x axis and 45 degrees around the y axis, what would the four values be?