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Technical Brief: Shadow Buffers Technology

 Shadow Buffers

VIDIA's GeForce4 Ti Graphics Processing Units (GPUs) are changing the face of lighting techniques for PC graphics by being the first to bring hardware acceleration for realistic shadows to consumer PCs. NVIDIA shadow buffer technology closes the gap between PC gaming and cinematic-style special effects for realistic, real-time shadows.

Until now, lighting techniques for real-time computer graphics were missing a key element: realistic shadows. Artists and photographers have always known the power of lighting and shadows. In fact, black-and-white film is still used for artistic photography because of the powerful effects that lighting and shadows, even without color, have on people. These same effects can be used to captivate users and draw them into real-time graphics environments.

The NVIDIA shadow buffer technique utilized by the GeForce3 Ti processors involves creating a map of which objects are lighted in a scene. This map is then stored in a shadow buffer so that it can be used later and accessed like a texture through the special shadow buffer hardware located in the GeForce3 Ti texture engine. This technique is faster and more hardware efficient.

  Notice how the wings on the spacecraft cast a shadow on other parts of the craft.  This technique is called self shadowing

NVIDIA Shadow Mapping Techniques
There are many techniques for rendering shadows, and each of them have their strengths. However, shadow mapping with NVIDIA shadow buffers has a number of key advantages over alternative shadow rendering techniques, including:

  • Complex Scenes—Shadow mapping works well for arbitrarily complex scenes containing many objects or complex shapes
  • Soften Shadow Edges—Shadow mapping can soften shadow edges using a proprietary shadow-filtering algorithm
  • Self Shadow—Objects can "self shadow." Note the wings on the spacecraft cast a shadow on other parts of the craft
  • Compatible with Multitexture Rendering—Stenciled shadow volumes can force multipass rendering, reducing performance if the application is either fill rate limited or memory bandwidth limited

Until now, shadow buffering was only available on professional rendering equipment, outside of the consumer's reach. With the addition of shadow buffer technology to the NVIDIA GeForce3 Ti GPUs, PC graphics get closer to replicating a real-world visual experience, closing the gap between PC gaming and cinematic-style special effects.