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Oblivion's Missing Physics
game: Elder Scrolls IV: Oblivion
posted by: Aaron Stanton
publisher: Bethesda Softworks
developer: Bethesda Softworks
date posted: 02:07 PM Sun Apr 16th, 2006
last revision: 02:41 PM Fri Apr 21st, 2006

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Click to read.How Oblivion Would Change if it Required Hardware Physics Acceleration:

The success of Elder Scrolls IV: Oblivion makes it the perfect example of what\'s missing from our current conception of next generation games. It is gigantic, consuming, and attempts to create a complete fantasy reality; for the most part, it succeeds.

Yet while Oblivion produces brilliant screenshots and still images, its environments sometimes seem insubstantial when seeing things in motion. It doesn\'t help the sense of realism when your character can run through foliage as if it doesn\'t exist, or that snowfall isn\'t affected by running, walking, or wind. Hitting an enemy with your 25lb sword results in little more than their mouth popping open in pain; for all its beautiful graphics, striking an enemy in Elder Scrolls IV amounts to slashing your sword through the air and listening for the noise that indicates you hit something.

Oblivion lacks Casual Physics, and the result is a splendidly beautiful world that still requires a blind eye in order to buy into the environment; it presses the visual appeal nearly as far as it can be pushed, and still can\'t pull off the illusion of reality, even a fantasy reality.

It\'s a perfect example of why graphics alone will not be the defining features of next generation video games.

It brings up the question: How different would Oblivion be if it were designed to require hardware physics acceleration?

The Difference Between Casual and Targeted Physics:

Oblivion isn\'t without a physics engine, of course. Once they\'ve passed their last breath, enemies crumble to the ground with a satisfying flailing of limbs. Items and weapons drop to the ground when they fall, and your arrows lose altitude as they travel.

Bethesda endowed Elder Scrolls IV with a robust targeted physics engine. This includes the rag-doll physics that govern how enemies die, and specific interactions in the game, such as when you drop a piece of armor onto the ground.

Targeted Physics result from a developer going out of their way to make sure certain physical actions come out right.

Casual Physics are the results of accidental interactions that happen as the result of a complex physics engine, but are not significant enough to warrant specific developer attention.

For example, if Oblivion\'s foliage bent as your character brushed by because each plant had its own physical characteristics that collided those of the leg, that would be casual physics. No developer set out to make plants bend as you pass, specifically, but the physics inherent in each object produced the effect.

Casual Physics occur when a physics engine is so expansive that no element of a game is immune to random determination.

And that\'s where physics acceleration comes in.

Why Physics Acceleration Will Define the Next Generation of Gaming:

The most impressive display shown at E3 2005 was not a game at all, but a technology demonstration by a company called Agia. Easily one of the most interesting companies in the game industry, Agia produces a line of dedicated physics accelerator cards designed to carry a computer\'s physics processes the same way a graphics card relieves the CPU of graphical calculations.

The impact of wide-scale physics acceleration in video games is going to be responsible for the next significant shift in how gamers perceive our industry. Good graphics won\'t be defined simply by things like dynamic lighting, but by the ability to play a game 100 different times without ever seeing a scripted scene that plays out twice in the same way.

The most impressive demonstration Agia had to offer is one of the most difficult to find on the Internet, possibly because it was the least visually impressive from a texture perspective. You can see screenshots of the demonstration:

Without seeing the interactive elements of the demonstration in motion, the screenshots hardly convey the excitement that comes with seeing physics acceleration in action.

In the technology demo, a ball was rolled through a clump of tall grass. Each blade not only bends out of the way realistically, but then slowly returns to an upright position. If a character had made the same journey, the footprints he would have left behind would slowly fade as the grass realistically returns to normal.

Another video I found impressive was this one here:

The house on the left is a rather poorly constructed model using only a few objects. The one on the right is much more complex, and uses several hundred objects that get blown apart and scattered as a result of the explosion. After this video was played for me at E3, the demonstrator pointed out that typical physics acceleration allows for tens of thousands of objects simultaneously, an order of magnitude above what\'s seen in this demo.

The reason I found this particular video impressive was not the complexity of the physics, but instead how much more substantial the second explosion looked compared to the first. Imagine playing Ghost Recon, only to have every building you hit dissolve differently depending on the direction you hit it from, and the size of the blast.

Oblivion\'s Missing Particles:

While Oblivion manages to deliver rag-doll physics, other physical interactions are glossed over. For example, snow effects are merely a mask that covers the screen; your own movement during a snow storm does not effect how quickly or at what angle the snow falls. In other words, the falling snowflakes never get closer to you as you move towards them.

This is done for a simple reason: the amount of processing power required to calculate the physics of each individual snowflake is too great for a system without a dedicated PPU (Physics Processing Unit) to handle. All the system\'s processing power would be claimed by physics calculations instead of texture rendering, A.I., and game functions.

An excellent example of this sort of problem playing out can be seen in this video of an Agia presentation:

Ignore the part about the rocket at the beginning of the video, and watch instead the demonstration of the rock slides. Each rock slide contains 6,000 individual objects cascading down a gully. The most interesting part of this presentation is the CPU and processing measurements; it\'s obvious that this level of physical interaction in a game is a dramatic strain on the system.

The same is true of Oblivion\'s snowflakes. Rendering the hundreds of flakes that would be required to make a snow storm seem realistic would be extremely difficult to do on a system without a dedicated PPU. However, with a PPU, there\'s no reason that snowfall couldn\'t realistically build up on the ground, allowing you to leave footprints in the snow that are gradually covered by additional snowfall.

With truly advanced physics acceleration, games will be capable of offering environments that are completely dictated by the laws of programed physics, not by the individual intentions of the developers. How your sword is deflected, and how a shield is moved, during an attack would be different in nearly every swing depending on the angle and the force of the strike.

Both the sword and the shield could be programed with individual physical characteristics.

Oblivion Offers the Best, and Makes the Perfect Example:

In terms of gameplay and visual presentation, Elder Scrolls IV: Oblivion is as near perfection as the industry currently has to offer.

Yet even with such advance visual effects and artistic design, the lack of Casual Physics leaves the player feeling removed from the world he or she is traveling in. This makes it the perfect example of why impressive visuals alone won\'t make truly next-generation titles. The imagery is realistic in a stand-still, and fake while in motion.

A truly next generation title is one that fundamentally couldn\'t exist on the systems that came before. They are not just revamped versions of titles that already exist, but with better graphics. For Nintendo these games will be a result of the Revolution controller, but for Microsoft and Sony, computational power will be the defining factors: complex AI and Physics will define what\'s truly considered next generation far more than visual appeal.

Once developers and gamers alike realize that, what we expect from video games will change. If video games were nothing more than inanimate screenshots, photo-realism would be an easier ideal to work towards. Unfortunately, photo-realism in the fluid and interactive environment of a video game is more than just a frozen image with good lighting, but is dependent on a huge number of factors.

It\'s time we spent some serious effort focusing on the factors we\'ve missed in the past.

Other Interesting Physics Information:

If you\'re curious about other examples and videos of realistic physics in action, here are a few links you\'ll probably be interested in.

Agia\'s PhysX Website:
Link: http://physx.ageia.com/footage.html

Agia currently sells a physics accelerator called PhysX. Their website lists games that currently have some sort of physics acceleration support (including Ghost Recon: Advanced Warfighter), and videos of additional physics examples.

The Unofficial AGEIA PhysX PPU Links & Info Page:
Link: http://personal.inet.fi/atk/kjh2348fs/ageia_physx.html#videosdownloads

This site is an extensive collection of links about and regarding the PhysX card and Agia. It includes direct links to tons of videos, photos, and a few interactive physics demos that you can download.

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