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MAYA实例：鸟类翅膀骨骼设定教程（英文）

If you have to make a wing yourself there are of course far simpler ways - the methods shown here were required specifically for the project in question.

It must be stressed from the outset that it is often near impossible to create a single 'Master' creature who performs all things for all shots. Much work on this project involved painstakinkly tailoring the structure of the bird for different shots. For the purposes of a tutorial however, it will be better to just cover this pre-vis/preparatory work which in the main, served as a template for later articulation and deformation structures within differing shots.

Firstly the feathers of the wing were modelled from simple nurbs planes. The possible particle approach involving sprites was initially discarded as fine localised control was required at the single feather level both in terms of texturing and animation. It was decided that for shots where the bird is small in frame, a proxy wing would be used - i.e. a simple flattened nurbs sphere in the shape of a wing and top projected with a matching texture of the feather arrangement.

The 3 pictures above indicate how the planes were built up in layers starting from the outer edge of feathers, the middle section, the front leading edge and finally the innermost layer (wing unattached) which would eventually blend the wing onto the body. The planes were carefully positioned one on top of each other by a fraction to avoid intersection. Also this would enable the opening and closing, or fanning of the wing during animation.

The textures were created in photoshop from actual scanned feathers and edited scans of library pictures and photographs of a pheasant (which we got from some farmer) for the project and kept 'fresh' in a refrigerator. Transparency maps were carefully made to provide fine detail at the ends of the feathers and areas of 'apparent nothingness' where the strands are separate and fine enough to give only a hint of actually being there at all. Scanned images were invariably warped in Elastic Reality to straighten and centre spines and also to uncurl photographs of the live pheasant.

The above render is an early test of the textured wing . You will notice that a duplicate (with upstream graph) was executed to create a second layer of feathers for each of the three divisions (outer, mid, front). These lower sets were also angled down a little, rotated in the x axis with the pivot at the leading edge to create a more filled out form as opposed to a thin wafer look when viewed side on.

Note also that the leading edge is starting to take on a very bunched, nebulous look that has become less well defined. This was done so that the front edge could eventually merge with an extrusion for an arm - effectively creating a 'bone' of feather as opposed to an obvious line of discreet units.

Next up, the skeleton for the wing was constructed. In total, 15 bones were initially set up to house groups of 1 to3 feathers at each level (outer, middle section and front). In this way, a single bone could be responsible for up to 8 or so individual planes at different levels of the wing but all in the same lateral group. This was the basis for achieving proper fanning of the feathers, both outward and inward when the elbow and shoulder pull the arm in close to the body or extend it straight.

The views above and below shows how the fanning bones were also split further into 3 discreet groups. Fistly the outer group which principally maintained the large, long outer feathers.

These have their own fanning properties during flight and spread out independently of the rest of the wing. They also follow the characteristic wrist action of a bird as it scoops the air backward at the end of the down stroke so they needed to be bound immediately below a discreet joint which would be the wrist (green circle below)

Secondly, the rest of the feathers (from just right of the middle of the wing to the left edge near the body) needed to be separated themselves to accomodate the elbow joint and make way for successful collapsing for the whole wing (circled blue)

The red indexed joint represents the shoulder and this would naturally give most of the wing flapping movement. The arm surface was also later bound to these 3 joints with a blend to the fingers. (For the purposes of this tutorial you may disregard the 2 intermaediate joints between the wrist and the fingers.)

Below shows us the final skeltal preparation for the whole wing to allow for successful fanning and collapsing with discreet feathers sliding over one another without intersection. Also with a 'semi-root' sholder joint for initial basic wing cycle animation and finally, an 'arm' section to allow placement of a feathery tube as the leading edge with extending fingers and claws.

The above image also shows the 'wing-attached' (leftmost) layer of feathers which are not bound so that they fan. Rather, they are bound straight to the joint above the shoulder so that they also do not move with the wing flap. You will see later how a lattice ensures that they form a smooth transition between body and wing during flight animation.

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