[x3d-public] [h-anim] Basic Animataion data

Leonard Daly Leonard.Daly at realism.com
Fri Nov 11 09:46:58 PST 2016

On 11/11/2016 7:40 AM, doug sanden wrote:
> ...
> Would like to see more goodies in HAnim / Anim.
> When implementing hanim in freewrl I was shocked by how little work the web3d browser does, and how much work is left for the content developer to do. For example IK. Q. Should we have a general IK solver node? Or other nodes to lighten the burden on content developers? Joe mentioned something about assigning joint weights automatically. Is that a node, or option in node?

Um, why?
X3D is not an animation application. It is a format and a run-time. 
There are already a number of animation applications that handle forward 
and reverse kinematics. X3D browsers (for the most part) cannot handle 
deformable skin. There may be some more advanced applications where it 
would be really nice to have IK, but right now X3D can't take baby 
steps. Content developers (from the art side) want to control the 
animation, it's programmers who want a node that says "walk" so they 
don't have to figure out how to do that animation.
Okay, so the above is a bit of a generalization; but there is so much to 
do with animation that we need to focus on getting a great foundation 
for the basics first.

> ...
> I'm not sure I understand the difference between maya and blender when it comes to root nodes. Isn't that something an exporter could add, if missing?
> ...

When rigging a model in Maya, you start with a single joint - a naked 
joint. You add another joint (making a "virtual" bone). This is the root 
structure of the model. You move the first joint and the entire model moves.

In Blender you start with a pair of joints and build from there.

I haven't worked enough with either of these packages to form an opinion 
on this. A joint always defines movement in relation to its parent; so a 
single joint can't define anything -- it's just a point. OTOH, it is 
symmetric to have everything go down to a single point. It's sort of 
like the fill-in squares game. Blender requires you to draw a line, Maya 
allows you to first pick a point.

Another thing I don't understand is scale. Given two points (joints) 
there is a line connecting them. This is the 0 rotation. Moving one 
point defines a rotation from the 0 to the current position. The 
distance between the points can also change. So where does scale come 
in? You can't scale-up/down a point. You can't scale the perpendicular 
size of the connecting line. You can only scale the distance, but that 
is the same a changing the translation. Alternatively, perhaps rotation 
and (distance)-scale should be kept and translation tossed. There are 
not as many degrees of freedom as there are quantities trying to specify 
the details.

*Leonard Daly*
3D Systems & Cloud Consultant
President, Daly Realism - /Creating the Future/
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