Here is the shape we will use as our spider body - simply make the Top viewport current, make sure you are on the Create panel, make sure Geometry is the type of objects you are creating, and that Extended Primitives is selected as shown in the image below. Select Capsule from the Object Type list, and use your mouse to drag a suitable sized capsule. Watch your Front viewport as you do this.
Now we focus on the Front viewport; On your Character pull-down menu, select Bone Tools. This will bring up the dialog box you see shown below. Click on Create Bones, as shown.
The image below demonstrates how bones are made; the right side leg of the character is complete, and we are in the middle of creating the leg on the left side of the character. Every joint is made by simply clicking the left mouse button. When you get to the end of the leg, simply right-click your mouse to end the process. You will see a little extra bone formed then, which is just fine. This little "nub", as I like to call them, is simply there to define the bottom-most joint of the bone. It is a fact that what is important with bones is not actually the bones themselves, but the joints in-between the bones. You will see this in action soon.
In the image below, we have gone a bit further; both legs have been created, and the body bone has been created as well. At this point in the process, we have turned on the Select and Link tool. This allows us to select an object and drag it to another object, and create a parent-child relationship. So, we can select the upper leg bone, as shown below (the selected bone is in highlighted white), with the left mouse-button held down, and drag the mouse to the main body bone (this is actually the spine), so that the upper leg becomes a child of the spine bone. Think about it - isn't that kind of how we are put together? Most of this hierarchy stuff is pretty logical.
The image below shows how the bones stack up, once you have made both upper leg bones children of the spine bone. The white arrow points to the Schematic View tool, which allows us to see how our various object are connected. Of course, here all of the bones have their default names, so it is a little unclear what is what. It's a really good idea to name your bones so you can see into the data better.
In the image below, we've selected the upper leg bone on the right side and then launched the Animation > IK Solvers > HI Solver. What we will do next, is to select the bone directly under the upper leg bone, to create an IK object that will help us to control the leg.
Here we've broken it down into steps because this process is a little tricky the first time you do it. Looking at the image above, and this image below, you should be able to follow steps 1-4 and create an i.k. object for the first two bones.
Here you can see the i.k. object sitting between the first and second bone on the right side.
Here below, we're about to do it all again - but this time we start with the second leg bone - then we add another HI Solver, and we will click the THIRD BONE DOWN. Look ahead to the next few images to get this clear in your mind before continuing.
Here is a shot of the bone we selected for our i.k. object placement; note that it is the third bone down, so it is not the nub at the end we selected. The i.k. object went to the bottom of the third bone, it went to the bottom of the bone we selected.
Below, we are using Select and Link once again, but this time we are using it on the i.k. objects themselves. We are making the "shoulder" i.k. object a child of the "foot" i.k. object.
Below, we are just finishing up the other leg - so in the end, we have two i.k. objects for each leg - one that controls what we might call the "shoulder", and one that controls the foot. In each case, the foot i.k. is the "master" - so if you move it, the shoulder will follow along.
Here below you can see we are testing the leg to see if it works right - we use the Move and Select tool, select the foot i.k., and move around to see how it looks.
Here we are using the Create panel, 2d shapes, and we are drawing a Line from where the leg connects to the torso of the spider to the foot of the spider. In the image below, we have drawn one line segment too many. If you want to stop your line, just click with the right mouse button.
In this image, both leg lines have been drawn, and we have also create two circles to define the size of the legs at the beginning and at the end. Also we have selected Compound Objects, activated the Loft tool, and have selected one of the leg lines for lofting.
If you scroll down on the Loft panel a bit, you will see "Get Shape". Click this button and select your largest circle. You should get a simple lofted object. But we will make a little more complex loft. See where it says Path, and Percentage. Since we have selected Percentage, we can scroll down the line we drew, till we are 100% of the way to the end of the line, and select "Get Shape" again. This time we can select the small circle. This gives us the lofted shape that is a little more like a real spider leg, thick at the top and thin at the bottom.
Below, under the Skin Parameters rollout, we are setting the Shape Steps and the Path Steps to 1, so that the leg will have less faces and be simpler to work with.
In the image below, we are selecting the body of the spider, clicking the right mouse button, and converting it to an Editable Poly.
Below, our spider body is still selected - under compound objects, we are launching the Boolean command....
Booleans are another feature that can be tricky the first time around. Now, in reality, it may not be the best way to attach a leg to a body, but here we are really concerned with keeping the process simple because the main thing we're trying to get across is how bones and skinning work. So, we will use Booleans because they are fast. Anyway, the image below shows two things - the operation type is set to Union, and the Pick Operand B button is active. This means you can now select the shape you want to union to the spider body. We will select one of our brand-new, lofted legs.
Now, Boolean will not let you boolean another object right away - you have to tell it you are finished first, by doing something like hitting the select button. That's what we are doing in the image below. Once this is done, launch the Boolean command again and boolean the other leg to the spider body so we will have one, complete spider body which has two legs.
Now we can select the new spider body and make sure it is an editable poly.
Now it's time to add a Skin modifier to the spider body. The blue arrow below shows where the modifier list is. With the body selected, click the down arrow on the Modifier List and locate Skin.
Here below we have scrolled down on the Skin modifier until we see the Bones: Add button. Click this button and select only those bones that would actually have a function in the character you are creating. This does not include "nub" bones, and certainly doesn't include non-bone objects like Circle01.
Here you can see that when you do this, the Skin Modifier's "Bones" list gets populated.
Here is the meat of how the Skin modifier works - under the Parameters rollout, you activate the Edit Envelopes button. Note also below that Envelopes are enabled. This means you can click on any bone in the bones list, or click on the black line that represents a bone in the Front viewport, and activate an envelope. Each bone has an envelope that defines that bone's area of influence. The bone actually can influence the vertices of the spider's body. So, if you can just figure out how to get each bone to control the right mesh vertices, you are well on your way to a rigged character.
We won't go into much detail about the envelopes for now, only to say that you can control them with the Move and Select tool - click on one of the black control points (they look like small squares) and move them to increase or decrease the envelope's size. Do this for every bone, until every vertex in the mesh has a bone that controls it. Some vertices will be at a place like a joint, where they will have an influence of two bones. That's expected.
Now use the Move and Select tool to move the spider foot i.k. and see if the spider mesh moves accordingly.
Now undo that last move, turn on the Auto Key button, go to frame 5, and move the spider foot i.k. up in the air a bit.
In this next image, we are selecting the spider body and moving it down a bit, as the leg goes up.
In this next image, we are rotating the spider body a bit on the same frame.
It sometimes helps to turn on your shading so you can get a feel for how this character will look as you animate it.
We hope this tutorial has been of help. Keep in mind there is a video tutorial that covers this same project in about 7 minutes