Evaluate a CURVE point from a percentage?

Coding Python Support
1

Hi,

is there a way to evaluate a curve point (world space) from a percentage (offset factor) ?

image

I only found the closest_point_on_mesh function but I cannot make it work:

dg=bpy.context.evaluated_depsgraph_get()1
C.selected_objects[0].pose.bones[0].constraints[0].target.closest_point_on_mesh(origin=mathutils.Vector((10,10,10)),depsgraph=dg)

Object 'NurbsPath' could not create internal data for finding nearest point

the object I am working on (selected/active) is a curve

>>> C.selected_objects[0].pose.bones[0].constraints[0].type
'FOLLOW_PATH'

>>> C.selected_objects[0].pose.bones[0].constraints[0].target.type
'CURVE'

thanks for your help

2

Off the top of my head, you could put an empty on the path with a Follow Path constraint, put the influence % where you want it, and get the location of the empty pretty easily

3

indeed, I used bones but that should do the trick (stupid of me)

not much doc around NurbsPath
I could also convert to bezier…meh

4

I cannot mod the offset_factor, the bones does not move

bpy.ops.object.mode_set(mode='POSE', toggle=False)    
endBoneConstraints[0].offset_factor = 0.6

I tried with empties, they all appear at the same position

for index in range(1,100):
        bpy.ops.object.mode_set(mode='POSE', toggle=False)    
        endBoneConstraints[0].offset_factor = 1/index

        bpy.ops.object.mode_set(mode='EDIT', toggle=False)
        empty = bpy.data.objects.new("Empty"+str(index), None )
        bpy.context.scene.collection.objects.link( empty )
        empty.location = (endBone.head.x,endBone.head.y,endBone.head.z)
5

I’m not sure why you’re using bones and setting the empty to them. You can just use a Path and an Empty, set the Path Offset with offset_factor, the empty will move to that point, and then you can get the location of the empty and do whatever you’re doing with bones with that location

6

the whole idea is to anim a bone chain a long a path
so I am open to suggestion, it should be a feature

spline ik cannot be animated

and follow path allows only one bone to follow the path

I need a mix of both features, I thought blender could do that easily in 2022

7

Couldn’t you use an IK constraint and just have the control bone follow the path?

8

I need the whole bone chain to follow that path
I mean there are tons of casse where this is necessary

a snake, a roller coaster, a tentacle, anything that follows a path

9

I’m pretty sure this is possible, I’ve definitely seen it done in Blender, but it’s a bit out of my depth as I’ve never personally done it. Hopefully someone comes along with a solution :slight_smile:

10

oh yes ! I made it
the issue was that I set the pose mode, while it apparently rather works in edit mode

the thing is that I have quiet a lot of bones, so I want to automatize the process :slight_smile:

1 Like
11

you can interpolate a biezer curve using mathutils

https://docs.blender.org/api/blender_python_api_current/mathutils.geometry.html#mathutils.geometry.interpolate_bezier

1 Like
12

thanks everyone for your support

13

now I just have to make the other armature follow that first armature

image
image2042×865 232 KB

I am sooo lazy lol…