Creating a Skeleton in 3ds Max - Part 2 - Leg Bones
With the spine and pelvis in place, in this tutorial you learn how to build the leg chains. You start by building one leg chain and then mirror it to build the other. You also learn about solving problems relating to mirroring bones.
- Recorded in: 3ds Max 2013
- This tutorial is intended for use with 3ds Max version 2013 or higher.
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With the spine and pelvis in place, it's time to build the legs.
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Make sure the Bones layer is current.
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In the left view, build a leg chain that has joints for the thigh, knee, heel and ball of the foot.
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Do not start it too close to the pelvis as you don't want it connected to that bone yet.
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Use the Bone Tools dialog to enable Bone Edit Mode and readjust the positioning of the joints.
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Oddly enough, the thigh joint should start pretty high, almost centered to the pelvis.
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A common mistake is to align it much lower, near the crotch.
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As you adjust the knee and the ankle joints, make sure you induce a slight angle between the thigh and calf bones.
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If you keep these two bones on the same line, the IK solver would eventually go crazy trying to calculate a solution.
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When you're done positioning the joints in the left view, reset the stretch on all leg bones and delete/recreate the end nub as you learned earlier.
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Press F to switch to the Front view.
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Obviously, the chain is centered on the construction grid; you need to move it to coincide with the character's leg.
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Exit Bone Edit Mode and select the thigh bone.
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Move the thigh bone to the right to coincide with the character's left leg.
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It is not yet aligned perfectly with the leg.
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Here, you have to be mindful of a very important rule:
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If you enable Bone Edit Mode, you DON'T want to break the linear plane onto which the thigh and calf bones are oriented.
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The knee is supposed to rotate in one direction only, mostly backward. You certainly don't want it to go sideways.
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By keeping the two bones on the same plane, you ensure the two bones stay together when moved sideways.
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You could potentially exit Bone Edit Mode and rotate the thigh to better adjust the position of the chain to the character's mesh.
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Right now, the calf and foot bones are not exactly centered to the geometry.
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Another method is to keep the chain pointing straight down, and make slight adjustments to the geometry.
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Unfreeze the Mesh layer and select the character.
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In the Modify panel, choose Vertex sub-object mode and select the foot vertices and include the ankle and the bottom part of the pants.
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Enable Soft Selection in Edge Distance mode.
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Set Edge Distance to 13 and the Falloff value to 35. This should create a nice falloff selection of the whole leg.
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The Edge Distance and Falloff values are based on trial and error as they change from project to project or from mesh to mesh.
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Using the Move tool in Relative mode, move the selection to the right (in X) to about 0.25 units.
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Now the leg mesh and bone chain are aligned together.
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Do not forget to repeat the selection on the other leg and move it left or -0.25 in X.
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It is important to keep the symmetry in the character.
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Exit Vertex sub-object mode when done and freeze the Mesh layer again.
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Rename the bones you have created.
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Use the names: Thigh, Knee, Ankle, Toe and Toe-nub
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Select the whole leg chain and use the Rename Objects dialog to force a prefix and a suffix as you have learned earlier.
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Name the suffix "_bone" as before but name the prefix "zombie_l_", with the additional "l" used to identify a left limb.
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With the left leg in place, you can now mirror it to create the right leg.
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It is VERY important to never use the Mirror tool that is in the main toolbar.
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This tool introduces negative scaling to mirrored objects that is bound to give you problems in rigs and in animation in general.
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Instead, you use the Mirror tool in the Bone Tools dialog.
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With the leg chain selected, click the Mirror button.
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Ensure the Mirror axis is set to X and the Bone Axis to Flip is set to Y.
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In fact, accept the defaults and click OK.
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A cloned chain appears on top of the original. You can move it to the side to see it better.
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To place it on the other side accurately, take note of the World X-Position value of the left thigh bone.
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Now select the mirrored thigh bone and invert the same value you noted a second ago.
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Again, remember how many times we stressed the importance of symmetry and setting up the scene around the center of the space.
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Consider the names of the mirrored bones.
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They're actually named exactly as the originals plus the "(Mirrored)" suffix.
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You need to remove that suffix and switch the "l" for an "r" to identify the right limbs.
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Select the right leg bone chain.
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In the Rename Objects dialog, enable the Remove Last option and set it to 10 digits.
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That will remove the "(Mirrored)"suffix which amounts to 10 characters including the parentheses.
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Choose also to remove the first 8 digits that represent the current prefix "zombie_l"
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Replace it with a prefix that reads "zombie_r" and click the Rename button.
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Verify that all bones are now named properly.
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Select both thigh bones.
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Choose the Rotate tool. Set the Coordinate System to Local in "Use Pivot Point Center" mode.
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As you Rotate the thigh bones in Local Y, they rotate towards or apart from each other in a nice effective way.
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In Local Z however, it would be nice to have them rotate together rather that against each other.
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In Local X, they're in fact rotating together whereas it would be nicer if they rotated opposite each other.
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So, out of the three local axes, only Y is working the way we want it. X and Z need to be reversed.
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Double-click the right thigh to select the whole right leg chain and go to the Hierarchy panel.
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Enable Affect Pivot Only.
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The Y-axis is the one working for you right now, so you need to do a 180-degree local rotation around that axis.
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It is best to use angle snap for this procedure.
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Don't mind the questionable look of the bones as you rotate them, they all fall back into place as you get to the 180-degree mark.
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Another method to rotate them 180-degree in Y is to set the Relative mode to the transform type-ins, and use a 180 value in the Y box and press Enter.
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Exit Affect Pivot Only mode and test the thigh rotations again.
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There is one additional item on the mirroring checklist to consider:
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If you select the right leg chain and reset the stretch of the bones, the bases of the bones now appear to be inverted.
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To fix that, you need to invert the Width and Height values related to bone sizes, in this case, -1 instead of 1.
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In the case of the nub, as usual, the safest way to operate it is to delete it and recreate it.
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You will need to rename the recreated nub to follow the naming convention you established.
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At this point, you have four bone chains in the scene, the pelvis, the spine and two legs.
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The pelvis represents the center of mass, so it makes sense to link the spine base and the thigh bones to it.
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This way, as you move the pelvis, the rest of the skeleton moves with it.
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Creating the arms will be the next stage in the process.