Introduction:
In this week’s blog, I’ll be talking about what we covered during this week’s lecture, where we looked at multiple methods of correcting our geometry whilst skinning, mainly focusing on fall-off joints and blend shapes. I’ll also be showing my process of completing this week’s workshop, where we had to add additional joints into our character rig, as well as using blend shapes and the pose editor for the first time.
This Week’s Lecture:
In this week’s lecture, we continued on from last week’s lecture where we focused on skinning. We began with a few lecture slides talking about corrective systems, where we looked at various methods.
Corrective Systems Options:
Fall Off Joints:
Positioned throughout the rig to help extend and blend the twist of geometry. For example, a forearm fall-off joint helps when the wrist twists side to side.
On-site Corrective Blend Shapes:
For example, using the Pose Space Deformer system in Maya instead of duplicating the mesh to create a blend shape.
Corrective Influence Joints:
A series of joints positioned and animated (SDK) to work with the movement of the rig – Maintaining volumes or adding additional effects.
Corrective Influence Geometry:
These can be as simple as a single plane of geometry or full muscle systems.
Off-site Blend Shapes:
Duplicating the mesh and creating corrective blend shapes or for additional rigging effects.
We also looked at the blend shapes deformed system as it’s used for corrective shapes to adjust the geometry. Our lecturer pointed out there are two different methods of using the blend shape, one is automatic and the other is manual. He mentioned the shape that is used to correct the model is the result of a subtracted shape (positive/negative shapes) to accommodate the skinned mesh. Even though Maya’s Pose Shape Deformer system does the job for you, our lecturer said it’s important to know how to do this process manually too. He demonstrated both methods during this week’s workshop, which was what we moved on to next.
This Week’s Task:
Our task for this week was to finish off the workshop we were doing during this week’s lecture. For the first half of the workshop, we focused on the different ways we could insert joints into a rig. Our task was to insert forearm and shin joints into the rig using any of the methods our lecturer showed us. In the screenshot below, is the default character rig that we had when we opened up this week’s workshop file.
I began by inserting a joint into the left forearm, using one of the methods our lecturer showed us. I selected the ‘Elbow’ joint and clicked on Skeleton > Insert Joints, and then dragged the new joint into the correct position,
To mimic the forearm joint to the right side of the character geometry, I created a locator where the forearm joint was, put it inside a new group, and changed the Group’s ‘Scale X’ to -1. This caused the locator to move on to the other side. I then inserted the second joint and snapped it to where the locator was positioned.
I then created the shin joints using the second method our lecturer showed us, where I duplicated the knee joints and moved them into the shin position. Whilst doing this, I deleted the ankle joints so I only had one joint selected (the new shin joint). Afterward, I parented the new shin joint to the knee joint.
I wanted the shin joint to rotate simultaneously to when the ankle joint rotates. I was able to do this by adding an expression to the shin joint’s Rotate X channel. I made sure that the Rotate X was equivalent to the ankle joint’s Rotate Y.
I repeated this step again for the other shin joint, as well as the two forearm joints. I made sure that the forearm Rotate X was equivalent to the wrist joint’s Rotate X.
Now that all the joints were added in, it was time to clean up skin weights. As you can see in the screenshot below, the geometry looks off as I rotate the wrist joint.
The reason for this is that the new forearm joint doesn’t have any influence at the moment as all of the weight is still within the elbow joint.
I selected all of the geometry within the forearm area, whilst having the replace button active and flooded the forearm joint, making sure weight had been taken off the elbow joint, and added onto the forearm joint.
I then smoothed the geometry, making sure there weren’t any rough creases. As you can see in the screenshot below, the entire forearm geometry now rotates as the wrist joint rotates.
I repeated this step for the shin and knee joints, making sure the shin geometry rotates properly as the ankle rotates.
During the second half of the lecture, our lecturer introduced us to blending shapes. He gave us a small demonstration using a sphere polygon. Afterward, he opened up the character rig again and showed us how to set poses for our model, whilst incorporating small tweaks to the model.
We used the Pose Editor to set particular poses. We began with the left shoulder joint, and then the left elbow joint. We only needed to do the joints on the left side of the geometry as we planned to mirror the poses at the end, meaning the right side shoulder and elbow joint would consist of the same poses. As you can see in the screenshot above and below, once we had set our poses, we were able to get back to our neutral pose by double-clicking on the neutral button inside the Pose Editor.
In the two screenshots below are examples of the poses being mirrored onto the right side of the geometry, where the user is able to go back and forth from their set pose to their neutral pose.