[Bf-committers] Collada: conversion from Joints to Bones

P. Visser p.visser at illusoft.com
Mon Sep 4 21:22:34 CEST 2006

Hi everybody,

I would like your opinion about the following issue:

As I said before, Collada works with Joints and Blender works with Bones.

Now I've got 2 problems when importing from Collada to Blender (Joints ->

I've created a picture to make it more clear:

1. When I import those 3 joints, I create 4 bones, so that each joint can be
rotated. In Collada, when using IK, when I grab joint2, joint3 moves as

However, in Blender there Is no 'root' bone (in fact, there are 2 root bones
now). When using IK on bone3, bone4 won't move. The only thing that moves is
bone1, so it's head is not on the same position as the head of bone2.

The only way to solve this behaviour is to add an extra root bone which will
be the parent of bone1 and bone2. I don't think this is a nice option.
(especially when exporting this scene again to Collada, because you end up
with an extra joint). As I have not much experience with animation, I was
wondering if the above problem is not an issue to you.

Also, when exporting the scene without the extra bone is a problem. You will
end up with 2 joints on the same spot as joint1. (one for the head of bone1
and one for the head of bone2).

2. Again, When I import those 3 joints, I create 4 bones, so that each joint
can be rotated.

As you can see at the table next to the images, in Collada vertice1 and
vertice2 are both bound to the single joint1.

In Blender there are 2 bones, so what's your opinion about what to do with
the weights of joint1. Should I simply divide them among the bones(bone1 and
bone2) created from that joint?

Thanks for the help,


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