Skinning

Applying the Skin Modifier….

In order to actually animate the character the previously created skeleton has to be attached to the mesh so that it can deform according to the bone placement. Firstly it was ensured that all earlier created bones were in the correct positions and centred inside the character mesh. A “Skin Modifier” was then applied which automatically assigns envelopes to each bone, i.e. vertices of the character mesh surrounding each bone are assigned to the bones movements. A similar modifier called the “Physique Modifier” could also have been used for this process, its advantages over the Skin Modifier are often debated however it is said that the Physique Modifier offers greater control when adjusting the envelopes and includes different features such as Bulge & Tendon editors. ^[1]

Given more time both of the modifiers would have been tested for their apparent benefits, however due to time constraints and other module commitments this was not conducted.

Initial Palm Envelope (Too Big)

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Envelope Adjustment & Vertex Weighting

From the example image above of the initial “Palm Bone Envelope” it can be seen that the envelope is far too big, engulfing most of the fingers and wrist rather than focusing on the palm area.The colour gradient ranging from blue to red signifies how much “Weight” is on each Vertex, in other words how much the bone is linked with them. Consequently each of the bones envelopes within the entire skeleton had to be adjusted to affect the appropriate parts of the character mesh. To aid the workflow of this process basic animation was implemented by enabling “Auto Key” on the timeline and each joint / bone combination was moved to preview the effectiveness of each envelope.

Testing Envelope Assignment with Basic Animation

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To fix the palm envelope for example all the unwanted vertices over the fingers and wrist were selected and then disassociated with the envelope using the “Exclude Selected Verts” button found under the “Weight Properties” rollout menu of the Skin Modifier. Similarly Vertices that were left behind once the bones were moved had to be weighted with the corresponding bones using the “Include Selected Verts” button. Adjusting the weight on each Vertex was immensely time consuming however it was necessary to improve the quality and realism of the end animation. Major problems were experienced during this phase as the rather complex character mesh made it extremely difficult to sufficiently weight and adjust each of the envelopes. Consequently the end animation is likely to suffer slightly, although it was felt that an reasonable effort was made in an attempt to fix these issues based on limited experience with this complex process.

Weighting Properties / Vertex Exclusion & Inclusion

Morphing Gizmos – Joint Angle Deformer

Another tool however was used to help the Weighting especially regarding overlapping/folding sections of the mesh around the knees, elbow and armpit areas. A powerful feature under the Envelope adjustment menu is called “Gizmos” and consists of three specific Morphing tools which are designed to fix these types of issues. The one that was implemented in this case was the “Joint Angle Deformer” which adds an editable Cage surrounding a selected group of Vertices allowing them to be pulled outwards to rectify the shape of each major joint in the mesh. These were applied to the knee, armpit and bicep joints to marginally reshape the mesh between bones when it is deformed by movements.

Knee Joint “Before” Joint Angle Deformer

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Knee Joint “After” Joint Angle Deformer

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Mirror Mode – Pasting Bone & Vertex Weights

Up to this point only one half of the character mesh was Weighted as effectively as possible. The other half of the bones still required envelope adjustment; to save having to repeat this involved process again a convenient tool known as “Mirror Mode” was enabled to copy the Weight and envelope properties to the other side of the skinned mesh. Once this button is activated each half of the character’s mesh is highlight either blue or green. Either colour represents each half of the skin modifier based on a chosen axis, defined by using the “Mirror Plane” dropdown selection box. Additionally the threshold of this mirror feature was adjusted to ensure all of the desired Vertices either side of the Mirror Plane were selected. The two paste tools were then used to copy both the Bone Envelopes and Vertex Weights from the left side of the mesh to the right, namely the “Paste Blue to Green Bones” and “Paste Blue to Green Verts” buttons found under the “Mirror Parameters rollout menu. The results of this mirror process can be seen in the images below, represented by the green and yellow halves of the character mesh. Yellow being the previously adjusted envelopes / weighted verts and Green displaying the affected half pasted to.

Mirror Mode Menu

Pasted Blue to Green Bones

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Pasted Blue to Green Vertices

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Although the Mirror process was somewhat successful it did not conduct a perfect job as either side of the mesh was not exactly symmetrical therefore some of the envelopes were marginally off. Another annoyance was that the Joint Angle Deformers were not mirrored and these therefore had to be recreated for the right side of the mesh which exhausted valuable production time. The skinning process overall was extremely frustrating especially regarding the character’s hands which were hard to rectify in terms of Weighting and Vertex association due to their intricate composition. Due to this the final animation will not look as realistic as originally intended, which is rather disappointing as a considerable amount of time was exerted towards these tasks.