Lumenex Engine Technical Brief.pdf

Technical Brief

Lumenex Engine:

The New Standard in GPU Image

Quality

November 2006

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Lumenex Engine: The New Standard in GPU Image Quality

November 8, 2006

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Introduction to the

Lumenex Engine

At NVIDIA we are extremely passionate about image quality. The people who

design our award-winning NVIDIA ® GeForce ® graphics processors hail from a

variety of backgrounds. Some came with experience in high-end workstation

systems, where thousands of fine lines had to be rendered with the uttermost

precision. Others spent their lives in CGI, where pixel shaders could run days on

end to produce the right subtle effects that made great films like The Incredibles and

Cars . When these engineers put their minds to design our next-generation

architecture—the GeForce 8800—they set out to build a GPU with the best image

processing engine in the world. They named the new technology the NVIDIA ®

Lumenex ™ engine.

Lumenex comes from the two Latin words luminosus and lumens . It symbolizes the

amazing quality of light—at once both bright and scintillating. Before the

introduction of the GeForce 8800 GPU Series, PC-based graphics chips could not

live up to this ideal for a variety of reasons. Chief among them was the conflict

between rendering well and rendering quickly; graphics processors simply did not

have the resources to render a scene in its most faithful representation without

slowing to a crawl. The result was watered-down images that were neither crisp nor

luminous.

The GeForce 8800 with the Lumenex engine solves these problems and raises image

quality to the next level. The new Lumenex engine brings several key innovations:

16× Coverage Sampling Antialiasing (CSAA)

16× near-perfect angle-independent anisotropic filtering

16-bit and 32-bit floating-point texture filtering

Fully orthogonal 128-bit high dynamic-range (HDR) rendering with all the

above features

A full 10-bit display pipeline

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Lumenex Engine: The New Standard in GPU Image Quality

Lumenex Antialiasing Engine

Since NVIDIA introduced multisample antialiasing (MSAA) to the industry in 2001,

gamers have embraced the new graphics possibilities with smooth edges and crisp

textures. Over the years we continually improved our antialiasing engine, bringing

features such as gamma-corrected antialiasing and transparency antialiasing for alpha

textures. With the GeForce 8800 architecture, we were given the chance to

completely rethink our antialiasing strategy and design a solution that sets a new

standard in interactive graphics.

The current method of antialiasing relies on using multiple subpixel samples to

calculate the color of object silhouettes. Storing and reading multiple samples from

memory requires a proportionate increase in resources as the number of samples

increases. For example, 4× multisampling requires four times the storage and ROP

bandwidth as standard rendering. NVIDIA GPUs, having been designed with

multisampling in mind, can perform 4× MSAA at high resolutions with little

performance degradation. However, to attain even higher quality, antialiasing

requires additional samples. This became infeasible on prior generations of

hardware.

The Lumenex engine was designed with one goal in mind: to provide the highest

image quality with the lowest performance impact. To realize this goal, we designed

an antialiasing subsystem that employs a new algorithm called Coverage Sampling

Antialiasing (CSAA). Unlike brute-force multisampling, Coverage Sampling

Antialiasing uses intelligent coverage information to perform ultrahigh quality

antialiasing without bogging down the memory system. CSAA is introduced in the

GeForce 8800 GPUs.

The Lumenex engine sets a new standard in antialiasing by raising the total number

of samples per pixel to 16—an ultrahigh quality often used in offline rendering. The

resulting images show lines with near-perfect gradient, dramatically reduced

shimmering, and unrivalled picture clarity.

In bandwidth-constrained scenarios, traditional GPUs slowed down drastically when

rendering with 16× antialiasing. The Lumenex engine, however, was designed for

high performance so the GeForce 8800 GTX actually performs 16× antialiasing at

nearly the same speed as 4× traditional MSAA. This is a significant breakthrough

for antialiasing in interactive graphics—for the first time, graphics can be rendered

at near-CGI quality antialiasing with real-time framerates.

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Lumenex Engine: The New Standard in GPU Image Quality

Case Study: Battlefield 2

Figure 1 is a screenshot from the popular game Battlefield 2 . The screenshot was

taken at 1600 × 1200, a reasonably high resolution. But as evident in the highlighted

boxes (please see enlargements in Figure 2), aliasing is still prevalent. This example

illustrates why aliasing cannot be eliminated by merely increasing the screen

resolution—there will always be lines and details fine enough to cause aliasing at any

resolution.

In the next section we see what a dramatic difference the Lumenex engine’s

Coverage Sampling Antialiasing makes to the image quality.

Image taken from Battlefield 2

Figure 1. Examples of aliasing

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