I was recently hired to animate a series of spiders for a music video. The shots were to contain anywhere from 1 to 10 spiders at a time crawling at a quick pace. In the past I had never animated a character with more than 4 legs, so this task seemed a little daunting at first. I set out to create a rig that was easy to handle and also offered a good amount of control over the character. By no means is this the only way or the best way to set up this rig, this is just how I decided to tackle this job. This tutorial was made for the novice or advanced user.
My first step was to model the spider. I've included a sample spider with this tutorial for those who don't wish to model one from scratch and would like to follow along. It is a low resolution Ubernurbs model which you should be able to manipulate in real time (it's near realtime on a G4 400Mhz with a Gig of Ram). I need a faster MAC :(
Lets start drawing some bone chains. You'll only have to draw 2 bone chains for the legs. 6 of the spiders legs are the same size. There are 2 other legs towards the rear that are larger, these 2 legs will need a different sized bone chain. Turn off all Groups except for the object you plan to add bones too. For this particular model I turned off all except "Left Leg 1". In the "Front View" window, start drawing your bone chain where the leg attaches too the spiders body, and starting a new bone at every joint. See Figure:3.
You should notice that in your "side view" that the leg bones aren't lined up correctly with the leg. Fix this by dragging the blue arrow along the Z axis to center the bones chain. See Figure:4. You should also name the parent bone of this chain for better organization. I named the parent bone "L Leg Chain 1". There's no real need to name the children bones, you won't be animating the bones themselves. It just helps to have the parent bones named.
Now looking in the "top view", drag the red arrow along the X axis to line up with "Right Leg 1". See Figure:7.
Now duplicate the "R Leg Chain 1" and repeat "Step 4" so that all of the spiders 6 smaller leg bones are in place. See Figure:8.
Now we need to draw our second bone chain for the 2 larger legs, "Left Leg 2", and "Right Leg 2". First, turn off the visibility for all legs and bones except the 2 larger legs, "Left Leg 2", and "Right Leg 2".
In the "Front View", start drawing the bone chain as before starting from where the leg would attach to the body. Then repeat Step 3, Step 5, and Step 6.
It's now time to bone the Spiders body so turn the visibility of all the legs and leg bones off. Start your first bone chain (that will consist of 1 bone) where the neck and abdomen meet and finish the chain by clicking at the back of the spiders abdomen. Then start a new bone chain (that will consist of 2 bones) starting at about the same place as the last bone chain. This time we're going to go in the other direction towards the head clicking once at the base of the head to create a joint and finishing up at the tip of the head. See Figure:11.
Our next step is too add a null which will control the body movement of our Spider. Go to Object / Add Null. We going to add our null in the "Side View". To create the null, start by clicking (keep the mouse button held down) at the top left corner of the head and drag down and across to include our neck bone and all of the head, then release the mouse button. See Figure:12. Again, in the "Top View" our null should be centered, if not, do it now. Now name the null "Mover". Now select all the body bones and color label them.
Note: You may skip Step 12 if you don't want to be able to animate the spiders teeth.
Step 14. Now we are going to add IK Handles which will drive the bones. To add an IK Handle, select "L Leg Chain 1", and then shift select the "Joint End" of that chain. Then go to Character / Add IK Handle, and now you have your first IK Handle. Repeat this step for all of the legs in order, this makes it easier. I have renamed my IK Handles accordingly, but this is not entirely necessary due to the fact that you will not be animating the IK Handles directly, but it will help a lot when parenting. Your "Camera View" should look like Figure:16 once you've added all your IK Handles.
You may skip Step 17 if you skipped Step 12.
Now we're going to add IK Handles to our Spiders teeth. Select the first bone in the "Left Tooth" chain and the "Joint End", and add an IK Handle. Do the same for "Right Tooth" and name the IK Handles accordingly. Lastly, parent the Teeth IK Handles to the "Head" bone. This way when you animate the head movement, the teeth IK Handles will not be left behind, yet you can still animate them. If you didn't bother to bone the teeth, then just parent the teeth themselves to the head bone and it will follow along with no problems. Your now done with the teeth!
Time to Bind the Skin of our Spider for animation. Turn visibility for all Groups on. Select all the bones in "L Leg Chain 1", Go to Character / Bind Skin to selected Bones. You'll be prompted to "Select Groups to be Skinned". Select "Left Leg 1" and then hit "cancel". Repeat this step for the rest of the legs. Make sure you skin the correct Group. If you make a mistake, you can always select the Group and go to Character / Detach Skin.
Now lets Bind the Skin of the Spiders body. Select all of the body bones (not the teeth bones)and go to Character / Bind Skin to selected Bones. When prompted to, select "Spider", and "Eyes", then hit "cancel". Then select the left teeth bones and Bind the Skin to the left tooth, and repeat for the right tooth. Now LOCK all Geometry/Groups. You'll only be animating the leg and body nulls, the "Abdomen", "Neck", And "Head" bones, and the 2 Teeth IK Handles.
Look at Figure:19 and you will see how clean and understandable it can be to do it this way. These elements are the only ones that need to be visible during animation. There are only 3 bones that have to be visible to animate. Cool huh!
Morly Arts © 2004