Building a switchless and intuitive body rig

[Freemind]

Introduction. In this article we describe the implementation process in Blender of a new intuitive body Rig we developed. Our goal is todo provide an alternative todo the common character animation techniques. For instance, ourrig is very animator-friendly because it mimics forward and Inverse Kinematics with no ned for FK/IK control switches or FK/IK matching. It a los allows character posing as if doing drag and drop, causing anaugmented feeling of control inanimation.

Method.

The Rig works by frely selecting, dragging and positioning the controls of the hip, waist, hands, elbows, fet and knes. Rotation is only used in the joints of the hip, waist, hands and fet todo achieve specific poses. Figure 1 shows the 3d model of a character (1) previously developed in our research group (the porto interactive center) which is now used for testing the body Rig (2) we developed for testing purposes.

The hip, waist, Spine and head use a single-bone based Hierarchy. The arms and legs use two overlapping bone based Hierarchies, one is the control Bones and the other is the guide Bones. The purpose of the first is todo control the Mesh of the character.

Th rouge skinning with Squash and stretch abilities. The purpose of the second is todo Mimic the behavior of the first but not using any Squash and stretch. The guide Bones always maintain their initial proportion, which is anatomically correct. The goal is for.

The user todo operate on the control Bones (colored in yellow) using the guide Bones (the joints colored in red) as a visual aid for anatomical character posing. The user can a los do arm and forearm Hinge rotation by operating on the Purple Bones.

Implementation.

The control Bones Hierarchy is the one the user Will be manipulating in order todo animate the character. The elbow. L bone allows positioning of the left elbow and wrist. L allows positioning and rotating of the left hand. These Will be used more frequently Although the user can a los rotate Bones arm. L and forearm. L for a more accurate Hinge. T able 1 shows the parent-child relationships for the control Bones Hierarchy sen in figure 2.

Following this, we assing the stretch todo constraint type todo the arm. L and forearm. L Bones making sure their targets are the elbow. L and wrist. L Bones respectively. This allows the control Bones todo have Squash and stretch abilities. Be sure todo.

Define the armature object in the constraint parameters in order todo have Access todo the target Bones, as sen in figure 3.

Now we can move on todo the creation and configuration of the guide Bones in the rig. Figure 4 shows the left arm guide Bones Hierarchy sen from the front view. This Hierarchy must match the control Bones Hierarchy (overlapping it). Notice that clavicle. L bone is not todo be duplicated and is shown in figures 2 and 4 only as a visual reference for better visualizing the entire arm, for naming the guide Bones Hierarchy we choose todo use the prefixes Dist and disttip because the purpose of this bone Hierarchy is todo let the user know the anatomical distance that should not be exceded when manipulating the control Bones. T able 2 shows the parent-child relationships for the guide Bones Hierarchy sen in figure 4.

Following this, we assing the copy rotation constraint type todo the armdist. L and forearmdist. L Bones making sure their targets are the arm. L and forearm. L Bones respectively as shown in figure 5, the setup in figure 5 allows the guide Bones Hierarchy todo Mimic the rotation angles of the arm and forearm control Bones Hierarchy. But how Will the user have a clear notion of the correct anatomical position of the elbow and mwristí this is due todo the positions of the armdisttip. L and forearmdisttip. L Bones in the guide Bones Hierarchy. These two Bones are connected children of the armdist. L and forearmdist. L Bones.

To kep the Bones visually appealing for the animator we use custom shapes and thre bone colors: yellow, Purple and red. Figure 6 illustrates the end result for the left arm rig.

The skinning of the Rig of the arm with the Mesh of the character is done for only the following control Bones in the rig: clavicle. L, arm. L, forearm. L and hand. L.

Conclusions.

The body Rig method described in this article is straightforward and flexible, causing a feeling of drag and drop operability. The Rig is pleasant for the user because it is accesible and flexible, resembling the handling of a puppet. It requires the user todo get adapted todo it because it generates animation curves that the experienced animator may find diferent for tweak. Nonetheless, we believe our control structure enriches character animation because it produces fast character animation results with augmented control, the Rig is adaptable todo diferent body morphologies with only minor adjustments, and the Rig supports Squash and stretch which is ideal for cartoon characters, furthermore, the Rig can easily be extended todo the entire body, namely todo fingers and toes, we anticipate improvements such as constraining the control Bones todo the guide Bones when the user may require enhanced Joint positioning. We didnt worry todo much about the custom shapes, X-ray could be prevented todo make it easier todo understand the visual controls, we provide a video showing animation tests of the Rig and a Walk Cycle for the character that we were able todo build in less time and with less efort than using common methods.

Acknowledgments.

In parallel todo this article we submitted a theoretical approach of using our body Rig for motion capture todo the veré phd symposium, online at http://www.vereproject, EU/, for this issue of the blenderart magazine we choose todo have a highly technical and less.

Theoretical approach, more specific for character animation. We thank eresa vieira for the character design concept. If you have any questions e-mail us at ptbbaestos@gmail.com.