View Full Version : Querying bone orientation problem

 SuperRune05 May 2008, 12:07 AMHi, I am scripting the alignment of an object to a bone. I need to copy the world z rotation of a bone to the world z rotation of a mesh object. If I open the Rotate Transform Type-In window (ref coord sys set to world), I see that the bone has a zero value in Z. However, when I query the bone using "in coordsys world radToDeg bone.rotation.z" i get a value of 28 something degrees. So as I align, the aligned object ends up with a wonky orientation. Is there any particular reason for this difference in bone rotation between the type-in tool and what the script sees? Thanks, Rune
SuperRune
05 May 2008, 09:17 PM
I solved the problem using vector math instead, creating a vector from the start to the end of the bone, and calculating the angle from that.

JHN
05 May 2008, 03:23 PM
Hi Rune, could you tell me how you retreive the end of the bone pos?

Thanks,
-Johan

SuperRune
05 May 2008, 08:10 PM
Hi there Johan,

In this case it was easy, I could just pick the position of the next bone in the chain :)

But here's a piece of code that might do the trick:
fn boneEnd obj =
(
-- Bone vector at origo
local boneVec = [obj.length, 0 ,0]

-- Align the vector to the bone
boneVec = boneVec * inverse (obj.rotation as matrix3)

-- Offset the vector to the bone
boneVec = boneVec + obj.pos

return boneVec
)

point pos:(boneEnd \$)

This works with the default bones I have in my 3ds max, but there are most likely cases where it won't work. So no responsibilities for loss of scenefiles or computers while using this function :P

Rune

JHN
05 May 2008, 08:24 AM
Hi Rune,

Thanks for the code, I did some work on it to account for scaling and stretching

fn boneEnd obj =
(
-- Bone vector at origo
local boneStretch = obj.transform.scale.x * obj.inode.stretchTM.scale.x * obj.length
local boneVec = [boneStretch, 0 ,0]

-- Align the vector to the bone
boneVec = boneVec * inverse (obj.rotation as matrix3)

-- Offset the vector to the bone
boneVec = boneVec + obj.pos

return boneVec
)

This is the code that I came up with myself, it's somewhat similar with different code.. my vector math is quit weak i hate to say...

(preTranslate o.transform [(o.inode.stretchTM.scale.x * o.length),0,0]).pos

Is freelancing working out for you, hope so...

Cheers,
-Johan

SuperRune
05 May 2008, 10:56 PM
I'm (sometimes) good with vectors, and now that I bought the Matrix Explained DVD that Bobo did, I hope I can finally get to understand matrices as well. Impressive you managed to condense it to one line. I tend to come up with solutions, but they're always kind of verbose. Glad it worked out for you :)

Freelancing has been fantastic so far! Struggled abit with RSI at the start, but that seems to wear off now. Things are looking really bright :D

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