# Essential Blender- P13

Chia sẻ: Cong Thanh | Ngày: | Loại File: PDF | Số trang:30

0
49
lượt xem
7

## Essential Blender- P13

Mô tả tài liệu

Essential Blender- P13: You may copy and distribute exact replicas of the OpenContent (OC) as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the OC a copy of this License along with the OC.

Chủ đề:

Bình luận(0)

Lưu

## Nội dung Text: Essential Blender- P13

2. Since the effect of a bone envelope is determined by these adjustments, you don't have vertex- by-vertex control. If you can get away with using envelopes for your armature, great! However, as envelopes are both less precise and somewhat slower than the other skinning method, for anything of middling complexity, it's necessary to assist envelope deformation with vertex groups. Vertex G roups A vertex group is a list of some of the vertices of a mesh. A mesh vertex can appear in as many different vertex groups' lists as you care to place it in, or it could belong to none at all. When using an Armature modifier that has the Vertex Groups button enabled, you can tell a bone to move part of the mesh by selecting vertices in the mesh and assigning them to a vertex group with the exact same name as the bone. For even more control, the vertices that are assigned to a group are given a weight. The weight, a value from 0.0 to 1.0, determines how strongly any actions performed on the vertex group will affect that particular vertex. For example, if one vertex appears in two different vertex groups (which happens a lot!) those vertex groups may be pulling their vertices in two different directions. Which group does the vertex follow? Well, if the vertex's weight in each group is 0.5, the groups have equal influence over the vertex, and it ends up splitting the difference. If, however, the vertex has a weight of 0.1 for the first group and 0.9 for the second group, the second group will have more influence, and the vertex will follow the second group's deformation much more closely. Vertex weights are always relative to the weights from competing groups. One vertex can belong to many vertex groups, and one vertex group can have many vertices, each with a different weight. Assigning these weights is often necessary for organic models, where joints are supposed to deform smoothly. Around a shoulder joint, for example, the weights might have to be adjusted so that the upper arm doesn't pinch too much when the arm is lowered. M anual Vertex G roup Assignment Figure: Vertex Group panel There are several ways to add vertices to a vertex group. The "manual" way gives you by far the most control. In Edit mode on your mesh, select several vertices. Under the Link and Materials panel in the Edit buttons, there is a Vertex Groups section. Click the "New" button to create a new, empty vertex group. Image:Dummy.png Figure RSD.18: The Vertex Groups controls in the Link and Materials panel of the Edit buttons. Then click the Assign button to assign the selected vertices to the just-created vertex group. When you click assign, the selected vertices are added to the vertex group's list, using the weight that is indicated in the Weight field.
3. Note: If you have changed the Weight control for any reason, either manually or through weight painting, and you click Assign, your vertices will use whatever weight is there, even if it is 0.0. It's a good idea to make sure that it is set to 1.0 before you create and assign a new vertex group. If a vertex group is not acting as you think it should, assigning vertices with the Weight control set to something other than 1.0 could be the culprit. Different vertex groups can be selected by choosing them from the dropdown box in the Link and Materials panel. Here are some of the controls for working with vertex groups: - Delete: destroys the vertex group. This will not delete the vertices from the mesh itself - remember, vertex groups are just a list of vertices. This button destroys the list. - Assign: adds the vertices that are currently selected in the 3D view to the active vertex group - Remove: removes the vertices that are currently selected in the 3D view from the active vertex group. If the vertices were not in the group already, this has no effect. - Select: selects any vertices in the 3D view that are assigned to the active vertex group. This adds to the current selection in the 3D view; it does not replace it. - Desel.: deselects any vertices that are selected in the 3D view and that are assigned to the active vertex group. Assigning Vertex G roups with W eight Painting Manually adding vertices to vertex groups quickly becomes tedious. Sometimes you need that kind of vertex-level control, but for more common use, you can graphically assign vertex groups and weights to vertices. This is done in Weight Paint Mode, which can be chosen on the 3D view header. Image:Dummy.png Figure RSD.19: Choosing Weight Paint mode. You should make sure that the armature is in Pose mode and that it is set to X-Ray so it will be visible through the mesh while you work. Upon entering Weight Paint mode on the mesh, it will change color (all dark blue if you haven't added any vertex groups yet) and the cursor will turn into a paintbrush. Image:Dummy.png Figure RSD.20: Hank ready for weight painting. How to A pproach Weight Painting Select the mesh and enter Weight Paint mode. Select a bone - even though the mesh is active, if the armature is in Pose mode you will be able to RMB select individual bones - and press the W-key. This brings up a confirmation for "Apply Bone Envelopes to VertexGroups." LMB click to confirm this and you will see the mesh change color. In terms of vertex group weights, blue means 0.0, red means 1.0, and the rest of the spectrum falls in between. This W- key option auto-paints the mesh with the influence of the selected bone's envelope, which is a good place to begin tweaking. In fact, if you plan to use vertex groups for your deformation, here's how to proceed: Turn off Envelopes in the mesh's modifiers panel and turn on Vertex Groups. Select the armature, enter
4. Pose mode, and use the A-key to select all of the bones. RMB click the character mesh and enter Weight Paint mode. Before directly selecting any bones, press the W-key and confirm that you want to "Apply Bone Envelopes to VertexGroups." Even though you can't see it, you've just had Blender create beginning weight paintings for every bone in the armature. Now, selecting individual bones will show you their weights on the mesh. Image:Dummy.png Figure RSD.21: The Paint panel for weight painting. The actual weight painting works by simply LMB dragging on the mesh model in the 3D view. The Weight control on the paint panel sets the maximum weight that the brush will paint. Opacity indicates how much of that Weight will be painted with each pass of the brush. Of course, the Size control indicates the size of the paint brush itself. Some people find it useful to enable the "Wire" option at the bottom of the panel, which superimposes the mesh's wireframe structure over the painted colors. If you find that you've made a mess of a particular vertex group's paint job, just press the "Clear" button to remove any weight painting for the selected bone. If you are working with a symmetrical mesh and armature, and the bones are named properly as described before, you can enable the X-Mirror option. X-Mirror allows you to weight paint only one side of a character, and have your painting mirrored to the other, saving you the trouble of duplicating your work on symmetrical characters. Clearing weights with the Clear button does not work symmetrically, regardless of the set up. With a bone selected, you can use the normal posing tools (rotation, translation) to transform it, letting you see how well your weight painting is working. In fact, you can set a pose on any or all bones, then continue to tweak your weight painting from there. The deformation will update in real time, giving you immediate feedback as to the quality of your work. If you have rotated an arm downward and see that the rib area is deforming too, you can set Weight to 0.0 in the Paint panel, Opacity to around 0.25 and start painting in the areas that deform too much. In this way, you can continue to weight paint, select and move bones to test, and tweak some more until the mesh deforms smoothly over the range of motion your armature will experience. Conclusion Armature creation, rigging and skinning are complex topics, and this is the merest overview of the relevant tools available to the Blender artist. Techniques for creating advanced rigs are constantly evolving, and can only be understood once you have a strong grasp of the basics. Included on the disk with this book are several rigs of varying complexity that have been released for general use. Some of them might function beautifully but be almost incomprehensible from a beginner's standpoint. Fortunately, the artists who created them have explanations and instructions for their rigs which have also been included on the disk. Perhaps the best way to learn some of these advanced techniques, besides sitting down with the artists themselves, is to study these rigs: pick them apart and see how they function.
5. Of course, you shouldn't feel that you have to create a rig from scratch every time you approach a new piece of animation. Many artists are quite content to use already-created rigs, and there is no shame in it. If you try the tools, though, and find that rigging interests you, you might be the person who creates the next great rig that everyone else is using! !
6. C hapter 7: Rigging and Skinning: H ands On By Roland Hess The best way to animate a complex mesh object like a character is through the use of Armatures. An armature acts like a skeleton: you actually move the bones of the armature and those bones drive the animation of the character mesh. The process of building an armature is called "rigging," and the process of attaching the armature to a mesh is called "skinning." Many artists are intimidated by the complicated controls and advanced functionality of the freely available Blender rigs and are put off from rigging altogether due to its perceived complexity. The armatures are excellent, and their creators have put great amounts of time and effort into making them flexible and efficient. It is possible, however, to create a fairly useful rig without creating dozens of hidden control bones. That is what you're about to do. G etting Started Open the file "hank_for_rigging.blend" from the "examples" folder on the included disk. Figure RST.01: The screen when you open "hank_for_rigging.blend".
7. This is the Hank mesh that you will be familiar with if you have already worked through Chapter 6. The first thing to notice before you even begin building an armature is that Hank has a rotation and a scale. Figure RST.02 It's always a good idea to begin working with character animation and armatures in a completely clean transformational state. With Hank selected, press Ctrl-A to apply the transformations, leaving Hank looking exactly as he does but removing the transformations. Figure RST.03: The Properties panel for Hank after applying transformations. T ip: Before working with armatures, use Ctrl-A to Apply all transformations to your mesh. Now that Hank is ready, create the armature.
8. Use the spacebar toolbox to Add->Armature. That new object sticking up from the ground at Hank's feet is a bone. Just like adding mesh objects to the 3D view, the armature and bone begin their existence in Edit mode, which will allow you to add and destroy bones, create parent/child relationships between them, and adjust their positioning to fit inside Hank's body. During this stage of armature creation, the Transform Manipulator isn't very useful, so turn it off by using Ctrl-Space->Disable or by clicking the pointing finger disable button on the 3D header. Figure RST.04: The new armature, with a single bone. With the manipulator gone, it's easy to see that the top ball of the bone (called the "tip") is yellow, while the bottom ball (called the "root") is purple. Yellow, as elsewhere in Blender, indicates that the tip is selected. You can see this by pressing the G-key to enter Grab mode and watching the tip move around as you move the mouse. Notice that as you move the tip
9. away from the root, the entire bone grows along with it. When you're done moving it, press the RMB or Esc-key to cancel the transformation, putting you back to where you were when the bone was first created. If you accidentally accepted the transformation with the LMB, remember that you can always Ctrl-Z to undo. One other thing to notice is that neither R-key rotation nor S-key scaling seem to have any effect on this single bone node. This bone will be the master bone for the entire armature, meaning that all other bones you add will be connected to it either directly or indirectly, so that when the master bone is transformed, the entire armature will follow it. You could leave it pointing up like this, but most people find that this sort of master bone is better visualized horizontally. Switch to a side view, and, using the G-key, move the tip of the bone back and downward until it lines up horizontally with the root of the bone. Holding down the Ctrl-key while doing the transformation will help you to get it right on. The length doesn't really matter, but you should make it stick far enough out behind Hank that it will be easy to select even during a cluttered animation session.
10. Figure RST.05: The tip of the master bone moved back and down.
11. RMB click in the center of the bone (anywhere on the bone except the tip and root balls) to select the entire thing. When you do this, more information appears in the Transform Properties panel, as well as in the edit buttons. One of those properties is the bone name. LMB click on the bone name, in either the Armature Bones or Transform Properties panel, and rename it "master." Figure RST.06: The bone renamed to "master." Notice how a part of the bone is hidden by Hank's feet? When you go to work on the rest of the armature, this could certainly be a problem. If the mesh hides the bones, how can you work on it? You could use the Z-key to toggle into wireframe mode, but there is a better way.
12. Figure RST.07: The X-Ray button. Enable the "X-Ray" button on the Armature panel of the Edit buttons. Now, the armature will always draw in front of the mesh. T ip: - When beginning an armature, add a master bone at the same location as the mesh object's center. - X-Ray will show bones that would ordinarily be hidden by a mesh. T he Spine, Neck and H ead You could add a bone for each and every vertebra in the spinal column, but fortunately you don't need that level of articulation. As Hank is a very simple mesh, just two spine bones, with one each for the neck and head, will suffice. Use the toolbox to add a new bone, with Add->Bone. When the new bone appears, RMB click on the main body of the bone to select the whole thing, then use the G-key to move it so that the root of the new bone rests near the pivot point of Hank's hip.
13. Figure RST.08: The base bone of the spine, moved into place. RMB select only the tip of the spine bone and move it to the small of Hank's back. Although the spine on a character like Hank would be flexible along its entire length in real life, if bent, it would mostly deform the body in two different zones: the upper and lower back. So, it makes sense to put the pivot point of one of your bones at that same point in the body.
14. Figure RST.09: The tip of the spine base, adjusted to the small of the back. From here, the rest of the spine is easy to construct. Hold down the Ctrl key and LMB click on the indicated areas in the illustration:
15. Figure RST.10: Ctrl-LMB click here to Extrude the base of the spine several times.
16. Ctrl-LMB clicking with a bone's tip selected extrudes new bones in a chain. If you've done it correctly, you will have something that looks like this: Figure RST.11: The spine, neck and head bones.
17. Your armature doesn't have to match exactly, but the crucial elements are that the neck bone's root should be at the rear base of the neck and that the head bone be very close to vertical. Before you go any further, press the A-key twice to select all of the bones. On the Armature panel in the Edit buttons, enable the "Draw Names" button. You will see that, with the exception of the "master" bone, the rest have fairly useless names like "Bone.001" and "Bone.003". By RMB selecting each of the bones in turn, and using the Properties or Armature Bones panel, change the names to "spine.base," "spine.top," "neck" and "head." Figure RST.12: The bones given useful names.
18. T ip: Ctrl-LMB extrudes a new, connected bone when a bone's tip is selected. A dding A rms Use Numpad-1 to change back to a front view. You could now create each side of the body individually, but that would be wasted effort. By enabling the "X-Axis Mirror" button on the Armature panel, you can have Blender help to create a symmetrical armature. Figure RST.13: "X-Axis Mirror" enabled. While X-Axis Mirror will mirror any transformations you make across the center of the armature as long as the bones are named correctly, it will not create the mirrored bones for you. You could create a single bone, then use the duplication and the M-key mirror tools to reflect it on the other side of the armature. This is such a common action, though, that the process has been shortened dramatically for work with armatures. RMB select the root of the master bone. You might have to MMB rotate the view to get a good shot at it. If so, be sure to use Numpad-1 to go back to the front view before continuing. Press Shift-E. Shift-E in armature Edit mode triggers a mirrored Extrude. Pull the extruding bone up and to the right until it looks like this:
19. Figure RST.14: A mirrored extrusion. Note: You may be noticing some differences in the way that your bones have "rolled" around their longest axis, compared to our illustrations. This should not cause any trouble, but if it bothers you, try selecting all of the bones and pressing Ctrl-N to fix their rolls. RMB select the right hand bone and move it to the top of Hank's chest. Then, select the tip of the same bone and place it where Hank's shoulder joint would be. The bone on the left side of the screen will follow everything that you do to the right. These will be the collar bones.
20. Figure: RST.15: The collar bone in place. RMB select the tip of the collar bone on the right half of the screen. It's now easy to Ctrl- LMB click at the elbow, where the hand joins the arm, at the start of the fingers, and at their tips. Doing so extrudes the bones to form the arm, and, with X-Axis Mirror enabled, the bone creation is duplicated on the other side for you.