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Archive Notice: This thread is old and no longer active. It is here for reference purposes. This thread was created on an older version of the flipcode forums, before the site closed in 2005. Please keep that in mind as you view this thread, as many of the topics and opinions may be outdated.
 
fab

April 10, 2005, 04:39 AM

right, i've got simple skeleton animations being exported from 3d max.
put the problem i've run in to is this:

i've only been testing skeleton animation where all the bones lay on the same plane. what i do is calculate the angle between the parent and the current bone, then this is made in too a quaternion which is then multiplied with all animation ke frame quaternions from the current bone. This means i can use the idendity matrix for all bones in my engine, i get the default pose.

but now i'm trying put bones in arbitary axis/planes. now when it runs through my code, it calculates the angle between the current bone direction, and parent bone direction for an offset quaernion. But when i go put this in my engine, it's all screwed.

Now i've had the idea of doing this 2 my offset quat:
instead of calculating and single angle/axis, maybe i need to project the direction vectors on to each of the axis', then calculate the axis/angle and create 3 quats and multiply them in 2 a single quat.

i'd just like to get some input from those that may have had similar issues, or experience in the area.

cheers.

 
juhnu

April 10, 2005, 05:12 AM

it's almost never a good idea to use angles in 3d. I definitely think that you should be using the concept of coordinate systems as a basis. (google for coordinate systems, matrices). After that it becomes really easy to calculate relative positions and orientations of the bone relative to the parent bone.

you usually do calculations using the 4x4 matrices which you can convert into a translation/quaternion pair if needed.



juhani

 
fab

April 10, 2005, 06:59 AM

i dont think just inversing out the parent matrix will mean that using identity matrix will give me the default pose (which is what i want) will it?

edit:
oh just tested it and it seems to be wokrking fairly well, other than some animations are roating around the wrong axis, this seems to be the way to go. cheers

 
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