From watching the videos of the polar bears it became apparent that most of the information I had concerned female polar bears rather than the males. Although the differences between the two are quite small, they do exist. The male bears are stockier and much heavier, so they would have to be animated accordingly. With this in mind I decided the most sensible thing would be to make my polar bear a female, and so build her with the proportions to match.

Before I could go about making the model of the polar bear I looked for pictures that would show me both the outside and the biology of the bear. I found pictures of polar bears in various positions and could therefore see how the different bones of the bear deformed in different situations. From looking at pictures of polar bears I was able to determine how to build the body in the right proportions so that it looked like an adult polar bear even though it was make out of blocks. 

I decided to make the behind and shoulders out of quite complex blocks compared to the leg blocks, so that they would appear rounder. I also decided to add enough detail around the head area so that the silhouette of the head looked correct, but not enough that it needed any detail around the eyes. This was so that the head did not look out of place with the rest of the body, and also so that the model would not look strange without a texture when it was finished.


Polar bears can lay their front paws down flat on the ground as added support when they lower their bodies.

They raise the back of the ankle up as they walk, however.
 


The skeletal pictures of the bear revealed where the ankle joints are placed to perform these actions.
 

With the skeletal information I could see where to break the blocks I had for the legs so that I could recreate the movements as accurately as possible. From the photographs of the polar bears it was obvious that the bear did not always use each joint separately, but sometimes used two at once to give the impression of one. This had been causing me some confusion in my design of the bear, but with a closer inspection of the skeleton I was able to make a far more accurate model that bent in all the right places.


The proportions of the legs of my first model were completely inaccurate.
 
 
 
 
 
 
 
 
 


I changed the proportions of the legs, and added in extra blocks to represent the front ankle joints based on the evidence of the skeleton pictures. This made the shape of the bear much more realistic.
 
 
 
 
 

Aside from the basic structure of the model I wanted to add some additional wobble to the belly and neck. Being as polar bears have a thick layer of fat and fur to protect them from the cold of the Arctic, they have a secondary wobble to their movement around these areas when they move. To recreate this I divided up the blocks that were representing the torso and neck into 4 pieces so that they could twist horizontally along the backbone up to the head, but also sway underneath. I added bones into these places so that I could control this movement.

I made one of the blocks for the belly wobble bigger than the other as most of the more violent vibrations occurred at the bottom of the belly.
 

The blocks for the neck wobble were more equal in size than the stomach blocks, as the wobble down the neck tended to be more of a twisting motion, which similar sized blocks could represent.
 
 
 

At the head of my polar bear I added bones in the jaw so that the bear could open and close its mouth. Although this would not be a huge part of the animations, a little mouth movement would make the bear seem more real, even if the movement was not noticed by the viewer.

Once I had made the body parts and decided where to put the bones inside, I decided that I wanted the legs to be controlled by inverse kinematics so that the paws would remain on the floor as much as possible. As I also wanted the shoulders and behind of the bear to slide past each other as it moved, so I decided to attach an IK handle from the shoulder blade or pelvis to the top of the legs, and another from the top of the legs down to the ankles. This would give me the effect of the shoulder blade and behind moving as well as allowing the legs to bend. I made sure the legs bent in the correct direction for the bear, which was achieved by biasing the bones in the desired direction. I did not want to limit the bones to only move in that direction, however, as I wanted the bear to be as flexible as possible for the positions I wanted it to get into. 

The ankles were connected with the IK handles in the same way. As polar bears have very flexible paws and ankles I did not want them to be constrained as a human ankle might be. From studying the video footage of polar bears walking, it was apparent that polar bears have a distinct way of rolling their front ankles as they move. This is so that they can move across the ice and snow as easily as possible without having to shift their weight too much. Although my polar bear was to be a simplified representation of a real bear, I wanted the movement to echo that of a real polar bear in essence if not by exact duplication. This meant that I wanted my bear to give the impression of rolling its feet, but did not need for the action to be anatomically correct. I therefore decided to have a basic IK handle linking the ankle and the ball of the paw, and the ball to the toes, but not to have any constraints so that it was left as an animation decision as to how I was going to represent the movement. 

I had at first limited the heel of the paws so that they moved in a similar way to human feet, but on closer inspection of the photographs of the polar bears in various positions, it was clear that the bears do not have the same constraints on the heel. In fact the heel of the front paws bear more of a joint resemblance to a human elbow where it can lay flat on the ground (as a human would do if crawling using the elbows as well as the hands for support), but also raise up onto the front of the paw (as a human would raise up to the hands).


The back paws are more reminiscent of human legs with more of a knee and ankle structure. I did not constrain the heel in this case either, however. Although the video footage showed that the back feet move forward onto tiptoe in a similar way as human feet, because of the skeleton of the bear having the blocks parented to them rather than bound, it would not really have been appropriate to limit the ankle in this way as the block would not distort properly and most likely result in an unnatural contortion.

Deciding What to Animate

Home