Simple question about animation

[benicourt81]

Hi,
I’ve an Egg file with a character who is walking
in Pview, he his walking and the character is going from one point to another.
I’d like him to walk but without changing his position (have the hike fixed for example).
Is there a simple method ?
I’m going to force the setPos of the bone hike (and i’dont know if it’s possible). Is it the good approach ?
Thanks in advance
Greg

[ThomasEgi]

you can use chickns synthetic root bone. it was made to solve exactly that issue.

i for my part simply add a new bone, and move that with linear interpolation over the walked distance. in the code end i use the same speed. works quite ok. it’s pretty much the same as the SRB above but hand-made.

for more information about the SRB please refer to the chicken manual

[benicourt81]

Thank you Thomas
I’ve found in the documentation :

Motion Extraction is a special feature that allows you to export animations where the character has displacement as if the character stayed in the same place, but it stores the displacements for every frame in the animation channel of a special bone and you can use this information in Panda3D to move your character appropriately. It’s perfect for things like walk-cycles so the character’s feet don’t slip, and many other cases where you’d like to keep your characters position clearly known without distorting the animation.
To enable Motion Extraction all you need to do is add a bone called SyntheticRootBone (which I’ll call SRB from now on) to the Armature used by your character. The SRB’s orientation and position are considered so if you don’t want your character rotated you should make the bone point in the +Y direction.
If the SRB doesn’t move the net effect will be the same as exporting without Motion Extraction so what you want to do is to place a Constraint on the SRB so it follows your character in some way. The most common behaviour of the SRB is as a ‘Ground Shadow’ that is, it follows the character in the XY plane. To do that just place a Copy Location constraint on the SRB as shown in the image.

I’ll test this solution
Greg

[benicourt81]

My problem is resolved, but i think, it’s not the solution of http://freefr.dl.sourceforge.net/project/chicken-export/Chicken/Chicken%20R42/test-modelR42.zip.zip

I’ve made an SRB which in the same spirit (i think).
The bone is following my model.

In panda, i’ve the bone X,Y,Z with self.srb.getPos():

self.srb = render.attachNewNode('srb-dummy')
avatar.exposeJoint(self.srb, 'modelRoot', 'SyntheticRootBone')

when i play the animation, the pos X,Y,Z of my avatar don’t change, but my SRB yes, relatively to the pos Avatar.
So, it’s easy to make him fixed at the screen with that.

But in the code of the example test-modelR42.zip, it seems not to function like that. The model is fixed, and the SRB is moving relatively, so to make him move at the screen, we must add the bone position to the avatar coord.

Why i don’t have the same ? I’ve forgotten something ?
[b]To be clear:

• The model of the example (fleur) is walking at the same place in Pview
• Not mine
  Why ? [/b]

In the doc:

The movement delta for the first exported frame will be calculated relative to the origin so make sure to do one of the following:

* Make the first exported frame be displaced relative to the origin as much as if the last frame in your animation were placed at the origin. 
* Export a reference animation that contains only the frame previous to your animation's starting frame in addition to your animation. If you do this you need the last frame's pose copied in the appropriate place to the frame just previous to your start frame.

I don’t understand, the fleur character in the example has only one animation, and at the first frame, it’s 0,0,0. But, in Pview, it doesn’t move while walking. It’s what i want.

[benicourt81]

Hi Thomas,
You have probably met the same problem with the position of the Bone used for calculate the delta of the animation.

i’ve the code :
srb = render.attachNewNode(‘srb-dummy’)
perso.exposeJoint(srb, ‘modelRoot’, ‘SyntheticRootBone’)

With that i can use the position of this bone to correct the position of my object

BUT : The position of this bone (srb.getPos()) is not good until it has been drawing to screen by the graphic card !
So, each time we draw the first frame (at each cycle of the animation), the position is not correct.

Look at this :
perso 1: 30.0 50.0 10.0 / 1.49240005016 1.55857002735 -1.50504994392
perso 1: 30.0 50.0 10.0 / -0.601334989071 1.78621995449 -1.50504004955
perso 1: 30.0 50.0 10.0 / -0.601334989071 1.78621995449 -1.50504004955
perso 1: 30.0 50.0 10.0 / -0.601334989071 1.78621995449 -1.50504004955

The first frame has been drawed 4 times and the very first time, it’s not good.
And again :

perso 49: 30.0 50.0 10.0 / -3.3917798996 -3.94430994987 -1.50504004955
perso 1: 30.0 50.0 10.0 / -3.3917798996 -3.94430994987 -1.50504004955
perso 1: 30.0 50.0 10.0 / -0.601334989071 1.78621995449 -1.50504004955
perso 1: 30.0 50.0 10.0 / -0.601334989071 1.78621995449 -1.50504004955
perso 1: 30.0 50.0 10.0 / -0.601334989071 1.78621995449 -1.50504004955

There is a solution to get the good position ?
Thanks in advance

[ThomasEgi]

@benicourt81

Hi Thomas,
You have probably met the same problem with the position of the Bone used for calculate the delta of the animation.

actually… i didnt encounter that problem. i dont not use the SRB at all.

in blender i make my animation. when i’m done, i add a new bone to my armature, and make it the parent of my armature i had so far.
then i take the distance between start and end point of my walk cycle, and add the same distance to the bone i just added in the opposite direction. then i set the interpolation for that bone to “linear” and export it. as a result. my model walks on the spot. in code i use the same distance as speed value for my walk distance.
that sollution is a bit manual but i my animation are very stable with no sliding over the ground.

[benicourt81]

oh, strange solution - but it functions, this is a good point.

My solution is good too, i thought it was the same of you because when fixing the Synthetic Root Bone, it doesn’t do the same that the chicken Egg Exporter documentation.

The Bone position is moving and i’ve only to do that :
perso.setPos(pos_perso-pos_srb) to have the walk on the spot (thanks for this expression).
but i must correct the position the first time the first frame is drawed. It’s strange…