I want to rotate a bone about it's own axis rather than the one of the world axes. I've tried using ang_add and ang_rotate but haven't achieved what I want. The picture below should indicate this. Suggestions? Thanks!

if(key_cul==ON) {pronation-=1;}
if(key_cur==ON) {pronation+=1;}
ent_bonereset_all(arm);
vec_set(off_axis_ang.pan,vector(0, 0, 20)); //Z' axis rolled 20 from Z axis
vec_set(elbow.pan, vector(pronation, 0, 0));
ang_rotate(elbow.pan, off_axis_ang.pan);
ent_bonerotate(arm,"bone2", elbow.pan);

some_angle += 5 *time_step;
ent_animate(me,null,0,0);
ent_bonerotate(me,"bone2", vector(0,0,some_angle)); //pan/tilt/roll so in this case you changing bone's roll but you want change bone's pan

So You should play with vector(some_angle, some_angle, some_angle) to check which one rotates your bone aroud axis you want to?

ent_bonerotate does NOT rotate about its own axis (unless there is some setting or some way to define this axis in MED that I am unaware of). ent_bonerotate uses the local axis defined due to rotations of parent bones, but not the axis of the bone itself. The code you suggested rotates the bone about the world roll axis when I try it (assuming I don't rotate bone1 first)

1. Post above edited
2. From manual:

Quote:

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Ent_bonerotate rotates an entity bone, it's childs and all attached vertices about it's hinge point. This is the normal rotate mode.
Ent_bonerotate_parent rotates an entity bone, it's children and all attached vertices about it's parent's joint. This corresponds to rotate3 mode in MED.

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"about it's hinge point" but given world pan/tilt/roll for its rotation. If I try rotating using pan, tilt, or roll, I get rotation about those axes. I need some combination of the rotations to get it about my arbitrary axis. ang_rotate and ang_add are supposed to be used for arbitrary axis rotations but its not working as I expect.

I understand that the rotation of a bone is defined about the hinge POINT of itself (ent_bonerotate) or of its parents bone (ent_bonerotate_parent), but the hinge point does not define the AXIS or AXES for rotation

There isn't an exact feature for what your looking for. You'll have to code it yourself.

- get the angle of the bone
- set temp to the target angle
- ang_rotate() the original angle by temp
- set the bones angle to result

Code:

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Function rotateBone(strBone, &cAng, &tAng)
{
    vec_set(temp, cAng);
    ang_rotate(temp, tAng);
    vec_sub(temp, cAng)
    ent_bonerotate(my, strBone, temp);
}

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strBone: Name of the bone.
cAng: Current angle of the bone. I couldn't find a function for getting a bones angle, so you may have to keep track of your bone_rotates.
tAng: This vector contains the relative angle to add to the current angle.