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Click on the “Select and Link” tool to make it active. Click-hold on the bone for the wiper blade to select it. With the mouse button held, drag the link-line over the bone for the wiper arm. When you release the mouse button the blade bone will be linked as a “child” to the arm bone (the “parent”). Like this:
Image 15
You’ll know this worked because both bones will be momentarily selected. When done, select the arm bone, and drag the link line out to the root bone. Again, both bones will be momentarily selected when the connection is made.
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Select the wiper object, and then click the “Modify” tab. Add a “Skin” modifier to the wiper object. You’ll need to first add the bones to the modifier. Above the empty “Bones:” list is an “Add” button. Click that, and then select the three bones you created. NOTE: ANY object can be used as a bone, so be sure you ONLY add anything but the bones, as in Image 16:
Image 16
Weighting
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Click the “Edit Envelopes” button in the Skin Modifier. We’re going to be working with the vertices directly, so check the “Vectices” check box. Also, uncheck “Envelopes” and “Cross Sections”. Finally, select the wiper arm bone (what I called “mcl650gt3_WIPER_BONE01”). You should see much of the wiper turns red. Your scene should look similar to this:
Image 17
Now, we want to select ALL the wiper object vertices (also shown in Image 17). Once done, in the “Weight Properties” section of the Skin modifier, enter a value of 1.0 into the “Abs. Effect:” (stands for Absolute Effect) text field, and press enter. The entire wiper object should turn red (Image 18). Again, this means that ALL of the vertices are now assigned to “arm” bone 01.
Image 18
Now, we’re going to assign the vertices that make of the blade to “blade” bone 02. I’ll also quickly demonstrate blended weighting when we do. You need to select bone 02 (“mcl650gt3_WIPER_BONE02”). Also, if your wiper blade is a separate element (as the one I’m demonstrating is) you can check “Select Element” in the “Select” section of the Skin modifier. This will let you easily select vertices by element (and you can CTRL-click to select multiple elements).
However you need to do it, select all the vertices required, and enter a value of 0.5 into the “Abs. Effect:” field. When you do, you’ll see the vertices turn orange, as shown below:
Image 19
Because you entered a value of 0.5, the vertices were only half-weighted to the blade bone. The remainder of the weighting is still assigned to the arm bone. Selecting bone 01 shows this more clearly:
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You may find there are times where some vertices need to blend between two or more different bones (as is often the case with organic objects). For our wiper though, we can fully assign the blade to bone 02. So, making sure bone 02 is selected, enter 1.0 into the “Abs. Effect:” field. The blade will turn red, as you’d expected.
Image 21
Now for the “ROOT” bone. The need for a root bone becomes more obvious for objects that you need to move around the scene, such as a walking character, a root bone makes this much easier to do. For a static object it will simply ensure the object stays put. Thus, it’s “good form” for each rig to include a root bone, hence why I included it here.
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