select joints at specific positions

[василий руков]

I have created alot joints perVertex, now i need select joints that on specific edgeLoop,
i can find vertex position, but how with that information find joints at this positions,
maybe it's simple, please help,

[vince touache]

if you created the joints yourself, by explicitely querying vertex n position and creating the joint on it, can't you generate a mapping list when you do it ? If it needs to be persistent, you could also tag your joint with the vertex ID

[Marcus Ottosson]

Seems like an interesting challenge. :)

from maya import cmds

def find_joint(position, epsilon=0.01):
    """Find joint at `position` with precision `epsilon`

    Arguments:
        position (tuple): XYZ coordinates to look for a joint
        epsilon (float, optional): Precision at which to consider it a match

    """

    for joint in cmds.ls(type="joint"):

        # Find worldspace position of joint, including parenthood
        p = cmds.xform(
            joint,
            translation=True,
            worldSpace=True,
            query=True,
        )

        if all(abs(p[axis] - position[axis]) < epsilon for axis in range(3)):
            return joint

    # No joint was found at this position
    return None

# For example..
positions = [
    (10.0, 10.0, 10.0),
    (50.0, 0.0, 0.0),
    (0.0, 10.0, 0.0)
]

# Create joints at these positions..
for p in positions:
    joint = cmds.createNode("joint")
    cmds.move(p[0], p[1], p[2], joint)

# And then retrieve them again
for p in positions:
    joint = find_joint(p)
    print("Found: %s @ %s" % (joint, str(p)))

# Test whether it fails when expected
assert not find_joint((999.0, 0, 0)), "There shouldn't have been a joint here!"

The trick being to (1) iterate over all joints, which isn’t free but also not too costly in any scene with < 10,000 joints or so and queries being made < 1 time/sec or so, and (2) compare their position with some “precision”. The latter being important because we’re comparing floating-point numbers, which cannot be trusted to exactly match with a float1 == float2 comparison. If you’re scene is very large, you would increase the size of epsilon to e.g. 0.1 or even 1.0 if it’s really, really large. If your scene is very small, then the opposite is true. 0.01 should hold up in cases where joints are placed with a minimum of 0.02 cm (default Maya units).

If joints are too close or epsilon is too large, only one of the overlapping joints would be returned, in the order provided by cmd.ls.

Is there a faster way? Possibly by replacing maya.cmds with maya.api, but I don’t think you can escape having to iterate over all joints like this which is where time is likely spent (although do profile it to make sure!), unless you do what Vincent suggests and store your joints up-front instead of relying on their worldspace position in the scene.

Hope it helps

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[vince touache]

haha I wanted to make sure there was no "smart" trick before going down the bruteforce road !

As soon as you start iterating on all joints / all vertices, it might quickly becomes too heavy to be usable. An "easy" way to speed up while not using the api would be to try.... cmdx? ^__^ 

If it is, indeed, meant to be used on "production" assets with a regular resolution, it could be interesting to consider using a data structure, like a kd-tree, to split the 3d space

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