Video Game 2D Animation Rigging Outsourcing

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2D Animation Rigging

So, you are making a 2D game and faced a problem with 2D animation rigging. We are here to save your day. Kreonit game art outsourcing studio is specialized on drawing and animating all kinds of game art: characters, objects, surroundings, UI, etc.

2d animation example

If you want to know how to outsource 2D character rigging — read further.

 

What is 2D Animation rigging

Animation rigging is the process of stuffing a 2D object with bones and assigning them to the object. This process makes the whole animation easier: the animator moves bones and the whole 2D object moves accordingly.

Before the rigging technology to become available, the animators had to make a frame-by-frame animation by hand. It was a hard and time-consuming job. So hard, that they had to draw only 20-30 frames per character to meet the deadline. Imagine, that you have to draw 30 images of a cat yawning, and keep all proportions the same.

For example, Metal Slug has outstanding pixel art animations, but the team spent almost 14 months to draw and animate main characters, enemies, surroundings and visual effects. It was worth the work, but nowadays, an artist with animation rigging may do the same in a few moths. If the artist has a ready to use assets, of course. In small conclusion, 2D rigging is the fastest and cheapest way to animate your game. 

 

Where 2d animation can be used

The best use case of 2D rigging is to animate characters. The players like when the character’s animations look expressive and there are plenty of different moves. For example, Dead Cells become popular not only because of fun gameplay, but also because every second weapon had unique animations and the main character movement was fluid and good-looking.

2d animated character

Also, 2D rigging can be used for hypercasual arcades or platformers. Other mobile games may benefit from 2D animated visual effects with lower GPU power consumption.

2d special effects

The third case of animation rigging is characters in dialogues, cutscenes, login and loading screens and other kinds of art.

 

How the animation rigging is done

Let’s take a look on 2D character rigging and animation. At first, the artist needs to prepare the assets. For character animation those are torso, legs, hands, hair and different pieces of clothing that are different from the body shape. For example, if the character wears a long coat and a hat with a long feather, that feather is better to be drawn separately.

2d character atlas

An image with all the body parts drawn separated is called the character’s atlas. So it’s important to tell artists that you need a character’s atlas for rigging, or they’ll draw you just a plain image. If the only asset you have is the unprepared character’s image, then artists can cut out limbs and redraw the missing parts. Despite it is time-consuming practice, we do this to animate backgrounds, wallpapers and login screens.

Then the animator rigs the 2D image: moves the limbs and clothing details in places where they belong and adds skeletal structure — bones. “Bones” in sprite rigging represent actual bones. The animator’s goal is to create a skeleton with joints, that will be moving like real ones.

On the next step the animator creates a mesh and ties it with the skeleton. Mesh in 2D animation is a polygonal net that connects the bones with character’s sprite. Precision is important, otherwise you’ll may get the character’s hair and hands moving simultaneously.

The last step is to add weight to the rig — to tell the animation engine how much influence each bone has on the mesh. It helps to make the sprite stretching look better and more natural. For example, when the character bends the knee, the cloth from behind the knee must shrink from both ways.

2d rigging example

And the rigging is done. Then the animators add bone motors to explain the engine how the joints must bend. The rest of the animations is done by programming motors. Some processes like clothes and hair bouncing may be automated, but the body movement is often made by hand.

 

Assets for 2D character rigging

If you are developing a game from the scratch for the first time, you’ll need to hire artists or apply for the game art outsourcing studio to make character concept art, final drafts and atlases. If you are going to draw art by yourself, then you’ll need these tips:

  • Examine the concept art and define what parts won’t be stretching with character’s movement. These could be metal armor plates, headwear, metal or wooden accessories, backpacks and other stuff. You need to draw these things separately, so they won’t stretch while rigging;
  • if you want to make a character non-symmetrical, for example with eye patch, shoulder tattoo or other unique details, you’ll need to draw character from both sides, so it will naturally turn in both sides. Also, it can be useful if the character holds something in one specific hand, like a sword or a gun;
  • fill the places where the limbs will connect to the body with according color. For example, the inner joint of the arm must be painted in skin color;
  • if your game will have outfit customization, draw the additional clothes on top of the body on the separate layer. In this case the game engine will just stack new clothes over the character model with no additional work from the animator.

If you don’t paint the atlas by yourself, you can use this list to know what to demand from the artist. Or just hire an outsourcing company like Kreonit — we have experience and won’t mess it.

 

Adding bone structure

In most cases, the bone structure of a 2D character will correspond with the actual human skeleton, e.g. the arm will have three bones: in shoulder, forearm and palm. But there’s no need to add 24 bones of the actual human spine to make good animation of the torso. Three bones will be enough.

2d rigging bone structure

Any other character’s piece of outfit which moves separately from the body will have its own bones for different animations. For example, long braid, headband’s ends, chains on hands and other things must be animated too. Let’s look at Dead Cells again: the main character has a long red cloth belt flying while the hero runs and jumps.

It may be funny, but the braid or headband will have more bones that the character itself. It is because their physics model must behave like a rope and not like two tied sticks. Luckily, those don’t need to be animated by hand. Unity 3D and Unreal Engine have a few typical algorithms to animate clothing and other decorative elements.

Finishing the bone structure

The next thing to do is to assign parental structure to the bones. The parental structure makes the bones of one limb to move together. It can be explained on tendons in our hands. If you try to clench one of your fingers, the other ones will also clench a little, because their tendons are connected to the same muscles. Parental structure works similarly: when the joint-parent is moving, its joints-children are moving too. Without parental structure the animators would need to move every bone manually. With parental structure all bones of the same group move together and naturally.

A character’s bone structure isn’t very complicated. An average character will have 15-20 bones and this amount will be enough. But the animator must have the skills to put the bones precisely where they belong to. It requires knowledge of the anatomy and a special science — the kinematic. Without this knowledge the bone structure and whole animations will look strange and unnatural.

Also, the more bones the character has, the harder it is to animate the body. For example, a detailed body like a character for a realistic fighting game will have a full skeleton with 3-4 bones in each limb. And the characters for an arcade game with cartoonish art style will need only 1-2 bones per limb. It’s easier to develop good animations for such a small system, than for a complicated skeleton.

 

Creating and weighting a sprite mesh

Just like a 3D model, a 2D game character with skeletal structure will have mesh, but in 2D. It is needed to tie the sprite to the bones, so the texture will stretch together with joint movement. Unreal Engine and Unity 3D create mesh automatically, but it is often needed to adjust by hand. For example, if the sprite clothing overlaps limbs, the software may accidentally unite them with polygons. In this case the clothing will repeat the limbs’ animation, and we don’t want that to happen.

Unlike the 3D modelling, 2D sprite mesh isn’t as complicated and skill-dependent. There’s no need to carefully count the polygons, because there will be less than 300 polygons for the whole sprite. Any modern smartphone will handle them without lags and FPS drops.

Then the animator weights the rig. It looks cool in Unity 3D: every bone has its own color, and the animator paints the sprite in them. The animator also has to decide the size of an area tied to each joint. Colors can be blended, so the particular polygons will be stretched and squeezed between one joint. You can imagine the weighting result as “gluing” the muscles and skins to the bones.

Weighting is the second most time-consuming process in 2D rigging, because the weighting is a trial and error method. In the end the animator produces a rainbow-colored sprite.

Remember about solid clothing elements that won’t need stretching? The animator doesn’t weight them, but connects them with joints to make them stay in place. 

 

Finishing the 2D rigging: adding bone motors

Bone motors control the movement of the specific bones or group of bones. Imagine a car wiper: they are placed on a small motor and can turn on a determined angle clockwise and counterclockwise. Bone motors work in the same way: they control how much the bone will move around the previous joint.

Bone motors have several helpful features:

  • they can be set in a specific way to tell the bones of one group how to react to the parental bone movement. It helps to automate the actual animating process and make the idle animations more natural;
  • bone motors must be set to not let the limbs move in impossible ways. For example, to bend the knees forward;
  • bone motors will allow the character to stand on uneven surfaces without one leg floating in the air.

And at this step the rigging is done. The animator now will make formulas for every animation. Those formulas mathematically describe how the coordinates of every bone should change with time. Thanks to this, the animations will look smooth both in 30 and 144 FPS.

 

Conclusions

The only type of game art style where 2D rigging won’t work is pixel art, because smooth animations and non-pixelated sprites will kill all the charm.

2D sprite animation is a fast and cheap way to add movement to your game. Thus, you need skilled animators to make it look good. We recommend you to hire an outsourcing team instead of freelancers because outsource studios are often more experienced with game-specific art.

And if you want the best possible result in a short term — hire us, the Kreonit game art outsourcing studio. We’ll animate any kind of art, from login screen like in League of Legends to 2D fighting game with dozens of characters.

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