Extension of the arm
Moving on, I want to add some contraction to the triceps as the arm is extended. Using the l_lowerArm_FK_ctrl, I posed the arm by rotating the X-axis by -20. I then duplicated the mesh, added some volume to the triceps and repeated the same workflow as for the bicep and the wrist. To drive the blend shape for the corrective shape for the triceps, I used the Rotate X-axis of the l_lowerArm_jnt and then the same again for the right-hand side.
Driving the triceps bulge with Set Driven Keys
Corrective shapes for the shoulder
Now we come to the shoulder region. I tend to create quite a few blend shapes in this region as there is always a lot going on. It's also important when working on the shoulders that there is a strong relationship between the upper arm and the shoulder and a lot of the time, you'll have to get the balance right with both parts working together. So first, I lower the upper arms and raise them to the horizontal position, creating corrective shapes for both positions. I then bring the upper arms forward and then backwards. At this stage, I'm mainly concerned about maintaining volume in the region and reducing the amount that the arm penetrates the chest. Then I focus on raising the shoulders that will in turn bring the chest inwards and up. After this, I rotate the shoulder back and add some further volume to the back. Driving the shapes, I used 2 main joints: l_upperArm_jnt and l_shoulder_jnt.
Correcting the area of the shoulders and the back with multiple corrective blend shapes
Corrective shapes for the torso and the legs
At this stage, the arms should be close to being finished. Next, we should add a few corrective blend shapes to the torso, the pelvis region and the lower leg. For the torso, I've mainly focused on adding some compression during lateral inclination.
Adding compression to the torso during lateral inclination
As the upper leg is raised, I went to town tidying up the pelvic region and softening the horrible crease that we had. Lastly, I cleaned up the lower leg by adding a corrective shape to reduce the amount the lower leg penetrated the upper leg.
Tidying up the results from raising the leg
Again, I've not gone into much detail here as the process has been covered in the previous steps. At this stage, I'm not too worried about adding every corrective pose as we can always add more during the animation process. As we animate the character, we'll also find that we may need custom corrective shapes built for a specific pose, but we'll cover this in more detail next time when we briefly look at referencing. Till then, happy corrective shape building.
Cleaning up the back of the knee with a corrective pose
Creating a symmetrical mesh
In this tip, I'm going to quickly cover how you can make your mesh symmetrical if it has some asymmetry present. As we have no clean UVs or textures for our mesh, this should be pretty straightforward. If the UVs had been created, we could do something similar, only we would need to perform some additional steps to copy the UVs from the old mesh to the new mesh.
First, duplicate the mesh you want to make symmetrical. In our case, this would be male_geo. Now, delete one-half of the mesh, select all the vertices down the middle, and pop a 0 into the X box for Absolute Transform. Now duplicate the mesh, plug a -1 into the Scale X attribute to mirror the duplicated mesh over. Select the 2 halves and go Mesh > Combine. Now select all the vertices down the center of the mesh and go Edit Mesh > Merge Vertices. A hard edge will now be evident down the center of the mesh. To get rid of the hard edge, select the mesh and go Normals > Soften Edge. Use the abSymMesh tool to check the symmetry and hopefully, everything should be hunky dory.
Making sure the vertices along the X-axis are perfectly centered
The next thing we need to do is skin the new mesh and then copy the skin weights over. Start by selecting all the joints in the male_bind_set and then Shift-select the new symmetrical mesh. Now go Skin > Bind Skin > Smooth Bind and use the same settings that we did for the initial bind. Now we want to copy the skin weights from our asymmetrical mesh to our new symmetrical mesh. To do so, first select the old mesh, Shift-select the new mesh and go Skin > Edit Smooth Skin > Copy Skin Weights. The default settings should do the trick just fine. Delete the asymmetrical mesh and you should be good to go.
Using the abSymMesh tool to check the symmetry of the model
Different tools to try out
This is not really a tip but I thought I would pop down some links to other tools to speed up the process of creating corrective blend shapes and to offer different methods of pushing skinning further.
poseDeformer by Michael Comet for Maya 2014.
Shapes by Brave Rabbit
LBrush by Joe Alter
Check out the previous chapters
Maya rigging: Introduction to rigging
Maya rigging: Introduction to rigging a human torso
Maya rigging: Introduction to rigging the neck and the head
Maya rigging: Introduction to rigging the shoulder and the arms
Maya rigging: Introduction to rigging the hands
Maya rigging: Introduction to rigging the legs
Maya rigging: Introduction to rigging the feet
Maya rigging: Introduction to rigging the fingers and thumbs
Maya rigging: Introduction to cleaning up the rig
Maya rigging: Introduction to skinning
Visit Jahirul's site
To see more by Jahirul Amin, check out Beginner's Guide to Character Creation in Maya
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