What's the angle? :)
Posted: Sun Aug 22, 2010 12:32 pm
I think a tutorial in how AS handles angles is needed. I'm going to only use degrees here, but of course the topic is just as valid for radians.
The following contains both info as I think it is, and questions about what I don't know.
First off, the coordinate system. angles start at 0 is east (or due right) and increase counterclockwise. This is consistent with math, but can be the source of problems, because it is also natural to think of north as 0 degrees and clockwise as 'positive' angle change direction.
Next, there is the notion of counter-clockwise vs. clockwise in rotations. I assume an increase from a lower absolute angle to higher absolute angle value means rotate counterclockwise, and a decrease indicates a clockwise rotation. Thus, I assume the system supports angles both negative and greater than 360. For example, to rotate counter-clockwise 40 degrees from 350 degrees one specifies an angle of 390 degrees. Likewise, to rotate 40 degrees clockwise from 10 degrees, one specifies and angle of -30 degrees. Is this correct?
Next, there is the notion of multiple rotations. If you rotate 360 twice you end up with same angle... so again the system must support angles outside the range 0-360 (i.e., a change of angle of +720 indicates a double rotation in the counter-clockwise direction).
Can this get out of hand (i.e., you have rotated something 10 rotations so it now has an absolute value of 3600)... assuming absolute angles is ever the way things are done, I'm not sure.
There is the notion of absolute vs relative. Some actions one wants to rotate to a SPECIFIC angle (absolute), and sometimes one wants to rotate RELATIVE to the current angle. Is there a way to specify in a rotation of bones or layers whether I'm asking for a RELATIVE or ABSOLUTE angle change?
Finally, are 'rotate layer', 'manipulate bones', and 'rotate bone' ABSOLUTE or RELATIVE operations (in terms of how it save the info)? This is important, since if it is absolute, adding a rotation beforehand would result in ending up at the exact same angle as before the add; but if relative, it would affect the final angle by the new amount.
It would be nice if one could choose which one is being specified (absolute vs. relative rotation). Maybe it is possible (like I've said, and probably will for at least another month, I'm new here...hehe)!
The following contains both info as I think it is, and questions about what I don't know.
First off, the coordinate system. angles start at 0 is east (or due right) and increase counterclockwise. This is consistent with math, but can be the source of problems, because it is also natural to think of north as 0 degrees and clockwise as 'positive' angle change direction.
Next, there is the notion of counter-clockwise vs. clockwise in rotations. I assume an increase from a lower absolute angle to higher absolute angle value means rotate counterclockwise, and a decrease indicates a clockwise rotation. Thus, I assume the system supports angles both negative and greater than 360. For example, to rotate counter-clockwise 40 degrees from 350 degrees one specifies an angle of 390 degrees. Likewise, to rotate 40 degrees clockwise from 10 degrees, one specifies and angle of -30 degrees. Is this correct?
Next, there is the notion of multiple rotations. If you rotate 360 twice you end up with same angle... so again the system must support angles outside the range 0-360 (i.e., a change of angle of +720 indicates a double rotation in the counter-clockwise direction).
Can this get out of hand (i.e., you have rotated something 10 rotations so it now has an absolute value of 3600)... assuming absolute angles is ever the way things are done, I'm not sure.
There is the notion of absolute vs relative. Some actions one wants to rotate to a SPECIFIC angle (absolute), and sometimes one wants to rotate RELATIVE to the current angle. Is there a way to specify in a rotation of bones or layers whether I'm asking for a RELATIVE or ABSOLUTE angle change?
Finally, are 'rotate layer', 'manipulate bones', and 'rotate bone' ABSOLUTE or RELATIVE operations (in terms of how it save the info)? This is important, since if it is absolute, adding a rotation beforehand would result in ending up at the exact same angle as before the add; but if relative, it would affect the final angle by the new amount.
It would be nice if one could choose which one is being specified (absolute vs. relative rotation). Maybe it is possible (like I've said, and probably will for at least another month, I'm new here...hehe)!