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Thread: "Growing Arms" technique needed

  1. #1
    Worst 3D artist ever Geoff Vane's Avatar
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    "Growing Arms" technique needed

    I have LW 11.6

    I need to create arms that grow, like Inspector Gadget arms.

    So, the arm section must be able to grow longer (and be animated if I need bends and such) but the hand must not be distorted and the fingers should be able to grasp something etc.

    I'm not good at lightwave.
    - I can do some legacy morphing (the "new" method keeps destroying my source object when edited)
    - I can do some very basic bones stuff. (I might be able to open and close a hand, maybe)

    I'm hoping to avoid "morph over bone chain" as this always goed wrong when I try it.

    Has lightwave evolved maybe and is there a more simple method to do this?

    I've got one week from 16 april 2018 to do this.
    All advice is much appreciated!
    Using LW since 1997 and still can't work with it...

  2. #2
    Look into joint bones. You should be able to do what you want with those bones.
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  3. #3
    Worst 3D artist ever Geoff Vane's Avatar
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    Okay!
    I found a spline method which might make it possible to animate along a path.
    However, I'm not sure if an arm with attached hand, can also grow along that path while keeping the hand undistorted.
    I actually want to start out with two hands, seamlessly connected by the wrist, and when the hands move away from each other, some primitive arm should grow between them.
    Should I create a morph sequence to put on such spline?
    Will bones in the hand stay in the hands?
    All things I don't know. I also am thinking it might be handy to have morphed hand stages in stead of using bones. I just don't know how to combine two morph actions: the arm growing and the hand shape.

    I've seen some joint bones which can stretch over the spline path. I still don't fully grasp why I need those.
    Using LW since 1997 and still can't work with it...

  4. #4
    If you use joints you can translate without stretching the hand. You could also make the hand separate geometry and constrain it to the end of your arm chain.
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  5. #5
    Man of many cells. shrox's Avatar
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    Where is a good joint tutorial?
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  6. #6
    Super Member vncnt's Avatar
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  7. #7
    Worst 3D artist ever Geoff Vane's Avatar
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    Interesting remark from vncnt. Probably cyber slang for explaining I'm stupid. Which is correct.

    I understand the separate geometry remark. But that would be a last resort. I dislike arms with some kind of glove at the end. It would look much nicer if it all was one smooth object. But I admit it's the hard way.
    Using LW since 1997 and still can't work with it...

  8. #8
    Worst 3D artist ever Geoff Vane's Avatar
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    I'm still confused: why would I need a bone chain for the arms when there is Spline Control? (I understand hands need bones to move the fingers)
    Using LW since 1997 and still can't work with it...

  9. #9
    I've never done a stretchy rig with spline control. If you want hands with bones then I think you'll need to find a way to mix both setups.
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  10. #10
    Lightwave Pimp Skonk's Avatar
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    One of the key reasons to use Joints is exactly so you can do stretchy limbs; it's what they are for.
    uh wha?

  11. #11
    Dreamer Ztreem's Avatar
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    Quote Originally Posted by Geoff Vane View Post
    I have LW 11.6

    I need to create arms that grow, like Inspector Gadget arms.

    So, the arm section must be able to grow longer (and be animated if I need bends and such) but the hand must not be distorted and the fingers should be able to grasp something etc.

    I'm not good at lightwave.
    - I can do some legacy morphing (the "new" method keeps destroying my source object when edited)
    - I can do some very basic bones stuff. (I might be able to open and close a hand, maybe)

    I'm hoping to avoid "morph over bone chain" as this always goed wrong when I try it.

    Has lightwave evolved maybe and is there a more simple method to do this?

    I've got one week from 16 april 2018 to do this.
    All advice is much appreciated!
    You say inspector gadget but you don't like glows and want a smooth transition between hands and arm. So you're more after a mr.fantastic from fantastic4 look than inspector gadget, am I right? Because I would use different techniques for the different looks. So to be able to help, we need to know the exact look. Is it only arms or is the arms attached to a character?

  12. #12
    Eat your peas. Greenlaw's Avatar
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    I've used DP Spline Deformer and LightWave's native Spline Control to animate tentacles, ropes, etc. (You can see my 2015 demo for several examples.) The idea is the make a deformable path you can control with a few position/rotation nodes that you can animate. Either tool works well, but I mostly use Spline Control because I can do a lot more with it.

    Unlike DP Sline Deformer, with Spline Control you need to create a bone chain for the deformation. You can animate the shape of the bone chain by animating the spline it's attached to. To make the arms extend through the bone chain, you can use a morph to 'stretch' the arms through the bones. Just be sure that Use Morphed Positions is enabled for the rig, otherwise this will not work.

    Hope this helps.

  13. #13
    Eat your peas. Greenlaw's Avatar
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    Just thought of something: If you need the deformation along the arm but not the hand, you might do better by scaling all the bones in the spline control path, except for the end bone where the hand is. You should be able to attach a full 'hand' skeleton there too.

    I haven't tried that with an arm, but I think that's what I did in the past with some creature effects to keep 'head' part independently poseable from the spline. (Sorry, don't have an example to show, but maybe these ideas are enough info to get you started.)

  14. #14
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    Perhaps some variation on the attached sample scene might work for you. Note that it is not a single geometry, but consists of four parts: a "Close Hand", the "Arm", a "Distant Hand", and the Curve from which the Spline in Layout is created.

    I didn't work at all on trying to make the "wrist" portion of the Hands conform to the diameter of the Arm or even try to make realistic looking Hands, but I think it shows the technique. BTW, I first tried Scaling the Arm Bones in the Z axis, but got some very strange deformations of the Arm along the Spline.

    This technique *might* work with a single geometry, having the Close Hand and Distant Hand bones not stretched along the spline. I started down that path but found managing all the bones in a single geometry to be really cumbersome.

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    StretchyArm_2_Sample_3.mov

    The basic technique is to use the Z Position of the Bones in the Arm to stretch it along the Spline. By selecting all the Arm Bones in Scene Editor (using right-click=>Selection=>Select child items (recursively)), setting their Spline in the Motion panel to the spline created from the Curve layer (Curve to Spline in Layout) and then changing all the Bone's Z position, you create the Arm stretching envelope you want. I found it *much* easier to enter a numeric value for Z position than trying to drag it out - the OpenGL overlay of all the rotation handles for the 100 Bones made try to drag it out very jerky.

    Note that the Bone's Z position is very small. When Convert Skelegons is invoked on the arm, each child bone is positioned at Z=0.1 meters from its parent. So, this scene initially starts with the Z position for all Bones at about 0.0 and ranges up to 0.1.

    Next, the Distant Hand is also set to the Spline in the Motion panel and moved down the Z Position to match the end of the stretching Arm. The Close Hand is also set to the Spline to match the spline rotation as it twists around.

    In this sample, the Spline nodes are animated over time to change the curve as the Distant Hand "grabs" something and withdraws. The Close Hand simply has an oscillating close / open cycle to demonstrate its separate rig / animation.

    The general process is to model the Hands, Arm and draw the Curve in a separate layer in Modeler. I use Skelegons to add bones to the Hands and Arm. For the Arm, I copy one of the edges of the Arm into a separate layer, center it on the Arm geometry, select the first two points, use right-arrow to expand the selection, and then Setup=>Convert Skelegons, finally deleting the Edge and cut-n-pasting the resulting Skelegons back into the Arm layer.

    The Hands have Weight Maps set up for each "finger" and the Bones for each finger have their Weight Map set in their Properties page. Finger bone animation was just done by hand (i.e. no IK).

    Good luck!
    mTp
    Attached Files Attached Files
    Last edited by MonroePoteet; 04-18-2018 at 01:04 PM. Reason: Numeric input on Bone Z Position; Small Z, Convert Skelegons

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