Stumbling Toward 'Awesomeness'

A Technical Art Blog

Wednesday, March 4, 2009

Common Character Issues: Attachments

I love this picture. It illustrates a few large problems with video games. One of which I have wanted to talk about for a while: Attachments of course. I am talking about the sword (yes, there is a sword, follow her arm to the left side of the image..)

Attaching props to a character that has to dynamically be seen from every angle through thousands of animations can be difficult. So difficult that people often give up. This was a promotional image for an upcoming Soul Calibur title, this goes to show you how difficult the issue is. Or maybe no one even noticed she was holding a sword. So let’s look at a promotional image from another game:

Why does it happen?

Well, props are often interchangeable. Many different props are supposed to attach to the same location throughout the game. This is generally done by marking up the prop and the skeleton with two attachment points that snap to one another.

In this case you often have one guy modeling the prop, one guy placing the skeleton, and one guy creating the animation. All these people have to work together.

How can we avoid these problems?

This problem is most noticeable at the end of the line: you would really only see it in the game. But this is one of the few times you will hear me say that checking it ‘in the engine’ is a bad idea. It’s hard enough to get animators to check their animation, much less test all the props in a ‘prop test level’ of sorts.

I feel problems like this mainly show up in magazines and final games because you are leaving it up to QA and other people who don’t know what to look for. There was a saying I developed while at Crytek when trying to impart some things on new tech art hires: “Does QA know what your alien should deform like? And should they?” The answer is no, and it also goes for the things above. Who knows how robotnik grips his bow.. you do, the guy rigging the character.

So in this case I am all for systems that allow animators to instantly load any common weapons and props from the game directly onto the character in the DCC app. You need a system that allows animators to be able to attach any commonly used prop at any time during any animation (especially movement anims)

Order of operations

Generally I would say:

  1. The animator picks a pivot point on the character. They will be animating/pivoting around this.
  2. The tech artist ‘marks’ up the skeleton with the appropriate offset transform.
  3. The modeler ‘marks’ his prop and tests it (iteratively) on one character
  4. The tech artist adds the marked up prop (or low res version) to a special file that is streamlined for automagically merging in items. Then adds a UI element that allows the animator to select the prop from a drop down and see it imported and attached to the character.


I can remember many heated discussions about problems like this. The more people that really care about hte final product, and the more detailed or realistic games and characters get, the more things like this will be scrutinized.

This is more of a simple problem that just takes care and diligence, whereas things like multiple hand positions and hand poses are a little more difficult. Or attachments that attach via a physics constraint in the engine. There are also other, much more difficult issues in this realm, like exact positioning of AI characters for interacting with each other and the environment, which is another tough ‘snap me into the right place’ problem dealing with marking up a character and an item in the world to interact with.

posted by Chris at 11:25 AM  

Monday, March 2, 2009

Make a 3D Game for the Right Reasons! (My SF4 post)

I ran out and got Street Fighter 4 (SF4) just like everyone else. Street Fighter was ‘the game’ you had to beat all the kids in the neighborhood at for an entire generation (sadly replaced by PES), and I have very fond memories of playing it.

SF4 is the first 3D game in the series created by Capcom, in the past, Street Fighter EX was developed by Arika, a company formed by one of the creators of the original game as well as many other Capcom employees. Even though porting the franchise to 3D was largely considered a complete and utter failure, they decided to give it another go, this time ‘officially’.

Strengths and Weaknesses

As artistic mediums, 2D and 3D are very different. 3D art is perspective correct, it is clean, sterile and perfect. It is much simpler to do rotations and transformations of rigid objects in 3D, this is why Disney started doing vehicles as cel shaded 3D objects in their later films. However, it is very difficult to add character to 3D geometry. As an example, think of Cruella Deville’s car from 101 Dalmatians, it has character. (When it’s not overly-rotoscoped from a real life model)

2D lends itself to organic shapes, which can be gestural, and are ‘rendered’ by a human being; so they’re never perfect. 3D is great for vehicles and space ships, anything that generally lacks character. 3D is also the only way you are going to get a photo-real gaming experience. For instance; when we were making Crysis, we knew this was the only way, there was never a question of which medium to use.

When I go on my ‘2D/3D rant’, I usually hearken back to something I love, so let’s take a look at the transition of an older game from 2D to 3D: the Monkey Island Series.

Many years ago developers felt that in order to compete, they had to ship games with the latest 3D technology. This is really unfortunate, and leads to them choosing to sometimes develop an ‘ok’ 3D game over a ‘beautiful’ 2D game. I believe in Curse of Monkey Island (last 2D title in the series (so far)), in the options menu there was an option to “Enable 3D acceleration”, upon clicking it, the words “We were only kidding” and other phrases pop up next to the radio button. The developers were already feeling the pressure to release a 3D game.

2D games are still profitable, just look at Xbox Live, where 2D games like Castle Crashers have been some of the top selling titles this year.

Lastly, lets not forget that 3D games are actually cheaper, or have been, historically. However, maybe not with some current-gen titles; where garbage cans have 4k texture maps and take two weeks to sculpt in Z Brush. But animation is definitely easier than it ever was. Of course the other side of that argument is that you can now have 6k animations in a game.

Street Fighter 4 Is A Three Dimensional ‘2D’ Game

Before going on, it’s important to note that in SF4, the characters still move on a 2D plane as they always have. It’s actually nearly identical to all the other games in the series as far as design.

As always, you are pitting your guy up against someone else, and both of your characters are the focal point, they are the only interactive things in a game which centers around them. This is a series that has always been about character, and has always been 2D with great hand drawn art. Remember: Capcom offered fans a 3D game and they did not want it.

So, SF4 is a game that takes place in 2D space and focuses on only two characters at any given time. This is great news, it means you can really focus on the characters, moreso than almost any other game genre.

The Constraints of a 3D Character Art Style

3D characters are driven by ‘joints’ or ‘bones’. Each joint has some 3D points rigidly ‘glued’ to it, because of this, 3D characters, especially in games, look rigid; like action figures. In my opinion SF4 characters feel like lifeless marionettes. In a 2D game, you can quickly and easily draw any form you want. The more you want to alter the ‘form’ a 3D character, the more joints it takes, and the more complex the ‘rig’ that drives the character. Also, on consoles, the number of joints you can use are limited. This is easily distinguished when comparing 2D and 3D art:

Notice how the 3D characters look lifeless? They don’t have to, it’s just more difficult. Whereas before, adding a cool facial expression meant simply drawing it by hand. Now it means sculpting a 3D shape: by hand. It’s tedious and difficult. Also, notice how in 3D Chun Li’s cloth is ‘clipping’ into her leg, or Cammy’s wrist guard is ‘clipping’ into her bicep. 3D is much more difficult to get right, because you are messing with sculptures, not drawings. You could also say the foreshortening on Chun Li’s arm in 2D looks weird; there are trade-offs, but in a 2D pipeline is also much easier to alter character proportions and fix things.

There are entire web pages dedicated to the weird faces of SF4 characters. It seems one of the easiest ways to make a character look in ‘pain’ was to translate the eyeballs out of the head: it looks ridiculous when compared to the hand-drawn hit reactions:

Whereas before you had one guy drawing pictures of a character in motion (maybe someone to color), now it takes a team to do the same job. You often have a modeler, technical artist, and animator, then hopefully a graphics engineer for rendering. That’s a lot of people to do something one person used to handle, and it introduces not only beaurocracy, but a complicated set of choreographed events that culminate in the final product.

This is a Capcom press image of Chun Li and it highlights my point exactly. It is harder and much more complicated to sculpt a form than draw it. Not to mention sculpt it over time, using complicated mathematical tools to manipulate geometry. However, it’s not an impossible task, and to think that this is ‘ok’ enough to release as a press image for an upcoming AAA game is crazy.

It’s not just deformation and posing, but animation in general. There is a lot of laziness associated with 3D animation. Let me be more precise: it is easier to ‘create’ animation because the computer interpolates between poses for you. As an animator, you have to work much harder to not fall into this ‘gap’ of letting the machine do the work for you. Playing SF4 you will see sweeps, hurricane kicks, and various other animations that just rotate the entire character as if on a pin. They also share and recycle the same animations on different characters, this was not possible in 2D.

One thing I find interesting is that, though the new game is 3D, it really has no motionblur. The 2D games had Chuck-Jonesesque motionblur drawn into the frames to add a quickness and ‘snap’, but it also adds an organic quality that is lacking in SF4.

EDIT: Having now logged a lot more time playing, there is indeed a weird kind of motion blur, it’s barely noticeable at all and looks almost hand painted/added.

Another odd thing, I can spot mocap when I see it, and I think the technique was used on some of the background characters, like the children playing under the bridge. The motion is so stellar that it puts the main characters to shame. That’s kind of sad. Though, all new characters introduced on the console seem to have much better animation, so maybe this is something Capcom have worked on more.

So Why Make A 3D Street Fighter?

If you aren’t going to make a game where characters can move through 3D space (no Z depth), why use a 3D art style, especially when it is harder to create expressive characters?

I will offer some reasons to ‘reboot’ the Street Fighter franchise as a 3D fighter:

  • Finally use collision detection to not have characters clip into one another as they always have
  • Use physics to blend ragdoll into hit reactions, also for hit detection and impulse generation; maybe allow a punch to actually connect with the opponent (gasp)
  • Use jiggly bones for something other than breasts/fat, things like muscles and flesh to add a sense of weight
  • Employ a cloth solver, c’mon this is a character showcase; if NBA games can solve cloth for all on court characters, you can surely do nice cloth for two.
  • Markup the skeletons to allow for ‘grab points’ so that throw hand positions vary on char size and are unique
  • Attach proxies to the feet and have them interact with trash/grass on the ground in levels
  • Use IK in a meaningful way to always look at your opponent, dynamically grab him in mid animation, always keep feet on slightly uneven ground, or hit diff size opponents (or parameterize the anims to do these)
  • Play different animations on different body parts at different times, you are not locked into the same full body on a frame like 2D
  • For instance: se ‘offset animations’ blended into the main animation set to dynamically create the health of the character, or heck, change the facial animation to make them look more tired/hurt.
  • Shaders! In 3D you can use many complex shaders, to render ‘photorealistic or non-photorealistic images (like cartoons)
  • You can also write shaders to do things like calculate/add motionblur!

Unfortunately: Capcom did none of these. Sure, a few of the above would have been somewhat revolutionary for the franchise, but as it stands, 3D characters add nothing to SF4, I believe they actually degrade the quality of the visuals.

EDIT: After playing more I have noticed that they are using IK (look IK) on just the head bone, shorter characters look up when a large character jumps in front of them.

posted by Chris at 12:15 PM  

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