Middlebury

Blender Rigging

Definition

Rigging is the process of creating guides for movement in 3D objects. It has its basis in hierarchical relationships between different movements in a human skeleton. What a rig does is define the way the various parts of a model will move in relation to the other parts of a model. Thus rigs are essential constraints to the types of movements different parts of a model can perform. To accomplish this functionality rigs have a highly complex system of hierarchical relationships. Inverse Kinematic target bones guide the bones around them by causing the bones following them to produce the opposite transformations the animator applies to them. Having this capability means that a good rig can be animated using only the target bones to produce movements that without a rig would be highly complex and time consuming.

Uses

The original purpose of rigs was to allow animators to model animal movements in a more efficient manner. Hence one of the most common reasons to learn how to rig models is so that a person can animate a human skeleton. Human rigs vary in complexity which is proportional to the complexity of the movements required by the animator. Indeed when making a rig it is good practice to minimize complexity. This requires a thorough examination of what is necessary for the animation. There are however uses for rigs other than for animating animals. Rigs are useful in any situation where the mesh itself will be animated. As opposed to the object. Hence many engineering models and physical models use rigs.

Guides

The Ball

This is a beginner rig which shows how a rigging can make animation easier

  1. Open Blender delete the default cube and add a UV sphere.
  2. In object mode deselect the sphere
  3. In top perspective add an armature shift=>add=>armature
  4. Switch to front view
  5. Select the armature and switch into edit mode
  6. Under the armature panel in the buttons menu turn on x-ray. This allows you to see the armature through the mesh.
  7. On the armature there are balls at the top and bottom which control the size of the bone. These are also the connection points between different armatures. The control points act like hinges between the various bones in the armature.
  8. Drag the bottom (the wider point of the bone) to the base of the sphere so that it looks like the picture below. 400 px
  9. Select the mesh and add an armature modifier. In the Ob: box type Armature. Typing the name of the armature determines what the modifier will apply to the mesh. This is the default name for all armatures. This can be changed in the links and materials panel.
  10. Now with the armature selected switch into pose mode.
  11. First select the armature then shift-select the ball now press control tab to switch into weight paint mode.
  12. Now turn the opacity of weight paint and the size of the brush up to 100%. Now paint the ball until it is entirely red. This will mean that all of the vertices are linked to that one armature. The ball will hence follow all rotation, scaling and translation that the armature undergoes. There are other ways of getting the mesh to follow the armature but this is the most transferable to other applications of armatures.
  13. Now switch back into pose mode, select the armature and move it to make sure that all of the vertices were weight painted.
  14. Now apply a key frame animation which has the armature going up and down and scaling into a squashed look at its lowest point.
  15. This should illustrate the basic way that a armature can deform and help in animating a mesh.
The Tree Trunk

This guide should give a slightly more practical lesson on the use of armatures. This guide assumes that you understand the process and terminology of the previous guide.

  1. Add a cylinder and scale it along its z axis so that it is very tall. Then add an armature and align the base of the armature with the base of the cylinder and the top of the armature with the top of the cylinder. Make sure x-ray is on so that you can see the armature through the cylinder.
  2. Now select the armature and press w until it is subdivided four times. The model should look like the the picture below. Trunk armature1.png
  3. Extrude one more bone from the tip of the armature. In edit mode under the "Armature Bones" panel deselect "con" and change child of to blank. Under BO: type target.
  4. Now in pose mode select the bone below the target and add a ik solver constraint. Under Target type Armature and then under under BO: type target. Then change the chain length to 3. This will mean that only the first three bones downstream from the target bone will be effected by its movement.
  5. Now Loop cut the mesh so that there are two loops contained within every bone.
  6. Select the mesh and add an armature modifier. In the Ob: box type Armature. Typing the name of the armature determines what the modifier will apply to the mesh. This is the default name for all armatures. This can be changed in the links and materials panel.
  7. Switch into pose mode and paint the vertices so that each section looks like the picture below. Trunk armature2.png
  8. Now move the target bone around to see the whole mesh deform in synch.
The Box Man

This tutorial is just an expansion of the previous tutorial. It will give the user a basic sense of how you make a human. From this point it should be fairly easy to move on to external tutorials which will provide more useful meshes and armatures to work with.

  1. Start with a cube then subdivide it then switch into front perspective and extrude it two blender units. Extrude it again 1 blender unit. Then extrude it two blender units.
  2. Select the one side of the ring of faces which is second from the top and extrude it two blender units then extrude it two more blender units. Repeat this on this opposite side so that you have something which looks like arms.
  3. Now we will make legs by selecting the left side of the base of the mesh. Extrude it two blender units then grab it and mode it over .5 blender units. Then extrude it again. Repeat this process on the other side. The cube man should look like the image below. CubeMan Mesh.png
  4. Now switch into object mode and add an armature. Then extrude it three times sizing each bone so that the third one ends in the middle of the arms. It should still be centered in the model as though it is part of the spinal column.
  5. Extrude once more to bring the fourth spine bone to the beginning of the head. Extrude one more time to make a head bone that breaches the top of the head.
  6. Now make sure x-axis mirror is on then shift extrude from the tip of the third bone up the spinal column. Move this bone out to create a shoulder bone. Then shift extrude twice more. The first extrusion should end mid-way down the arm. The second should end at the tip of the arm. Follow a similar procedure with the legs. Except also add two bones sticking out to the sides at the base of the legs. The final armature should look like the image below.

CubeMan Armature1.2.png

  1. Now select the mesh and subdivide it twice.
  2. Select the mesh and add an armature modifier. In the Ob: box type Armature. Typing the name of the armature determines what the modifier will apply to the mesh. This is the default name for all armatures. This can be changed in the links and materials panel.
  3. Change the head into a target bone by selecting it in edit mode and naming it headtarget. Do not disconnect it but do change its parent to blank. Do the same thing for each of the foottargets but name them foottarget_L and foottarget_R.
  4. Now in pose mode select the bone below the target and add a ik solver constraint. Under Target type Armature and then under under BO: type headtarget. Then change the chain length to 5. This will mean that only the first three bones downstream from the target bone will be effected by its movement.
  5. Also make each of the leg bones next to each of the foottarget bones an ik solver set the chain lengths of these bones to 3. Again chain length determines the number of bones up the up the hierarchy from the ik solver that will be transformed by the ik target. In the case of the legs two bones would mean that only the hips moved.
  6. Using the process described above go into weight paint mode. And paint the areas that overlap with the individual bones. Some overlap between bones is fine.

Links

For a complete guide at human modeling follow this link to Blender Summer Of Documentation character animation tutorial.

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