Another Anti-distortion technique

Thanks to shadowfeign on the OGRE3D Forums, another technique to limit animation distortion has come to my attention. Via modeling the joint at a 45 degree angle. However, for joints such as elbows, where the final angle is more than 90 degrees, deformation will be visible once again, but by applying it to joints such as the fingers, you will have much less work to do on the final tweaks. (Removing the bones that follow the real skeleton that have no vertexes attached to them that are there only to create the final bone layout)

View his video:

Case Study: Limiting animation distortion

With any 3d model, if you are using a bone only animation, there will be a certain amount of distortion at the joints. This is quite apparent with low poly models. Although there is an acceptable limit, based on how small the part will be on the screen and how much the bone bends, it is good to know how to set up things to limit said distortion. In this example we will look at the fingers on Ethan's hands. In the left example, you can see that when the fingers bend, they begin to thin, while on the right, a technique was used to make the fingers stay close to their original thickness. Lets look at that now.


Here we have the original bone setup: bone joints in the center of the vertexes that bend.
As you can see below, one method of removing part of the distortion was to add another layer of vertexes, and make sure the part of the finger stays the same size. This works to an extent, but with a way that I found, I create a better look with less vertexes.

Below, you can see the new bone set up, and the vertexes are assigned to the new bones. The bones originate from the center of the joint, and extend to the top of the joint. A constraint is added to make the bones rotate 50% of the old bones, and then the length of the bone (local-y) is scaled as the bone rotates to compensate for the distortion caused by the rotated vertexes. At this point, I am not sure of the ability to export local bone scaling, however if the current format doesn't allow it, I can always create my own. Right before export, the bones that don't have any vertexes assigned to them are removed, to make sure they do not affect the speed of the model.

Low Poly Facial modeling for advanced animation

The face is the most important aspect of a character. People look at faces all the time, if something is off, you can just tell. Out of the almost 2k polygon Ethan Bridger character, with independent fingers, almost 600 polygons belong to the head alone. What you see in the picture above is half of Ethan's face, half of his teeth and mouth chamber, and his eye.

The Lips:
Pay attention if you will, to the corner of his lips. There are a few extra polygons that need to be discussed. They are there for animation purposes that seems to have been widely overlooked. When you smile, a crease forms between the lips and the cheek area, and you have to have enough polygons to define that crease for the smile. Without the crease, the smile looks smaller than it is. If your character isn't ever to smile in the game, then remove these extra polygons.

The Mouth:
The mouth has no tongue, to save polygons and isn't exactly attached to the lips. The attachment isn't necessary as the lips never go below the teeth on Ethan when he talks. The teeth are just one curved block that will have a displacement map attached to it to give it extra detail, and the mouth's chamber is only there to make sure that you will never see the back of the neck through the inside of the mouth.

The Nose:
Not much to tell here. All you need is the basic shape of the nose, not too high def. extra detail will be added later with the distortion maps.

The Eyes:
The eye is just a sphere with the back end cut off. For animation, the bone would start where the center of that sphere would be, and end at the eyes tip. Further on the eyes, never let the eyes stand still, use a combination of constant head movement and slight eye movement to give your character more life. Otherwise, you will just get a cold stare. Also, an empty object is a great way of making sure that the eyes are aligned with each other when creating your animations by adding a track to constraint on the eye's bones.