In MultiBuffer PowerVision configurations, the frame buffer subsystem contains the
necessary VRAM to support the real-time accumulation buffer. This buffer is used to
combine or accumulate a set of scenes. The Graphics Library also allows for a
weighted blend of each of the scenes into the accumulated image. The weight of each
scene is defined by the user. These weights can be used with other features of the
graphics subsystem (projection matrix) to define User-Programmed Filter Functions.
Many useful effects can be generated using this buffer.
As each frame is accumulated into the buffer, a more accurately sampled image is
produced. The user can choose to render fewer frames to support real-time
constraints or to render many frames to obtain a high-quality image.
Multi-Pass Spatial Anti-Aliasing renders the same objects for several frames while
moving them spatially. By jittering the subpixel offsets (that is, projection matrix) and
accumulating the scenes together, an anti-aliased image is rendered. The user can
choose a desired filter function to define the weights for each pass.
Motion blur is accomplished bv a technique similar to the spatial anti-aliasing
method. Instead of changing subpixel offsets, the geometry is allowed to move as the
image is being accumulated. Motion blur results when these still frames are blended
By modifying the projection matrix as images are accumulated, viewing the scene
from various points across the aperture of a lens, a depth of field image is created.
Objects further from the focal plane of the lens are blurred while closer objects are
An Image can be quickly filtered using the accumulation buffer. Since the user has3.3.12 Orthogonality
control of the weighted accumulation of each image, and since the image can be
moved about on the screen in multiples of pixel coordinates, the accumulation buffer
can be used to convolve the image by means of many filtering techniques.
The accumulation buffer provides a solution for spatial aliasing, motion-blur, depth of
field, and penumbra. Another feature of the accumulation buffer is that all these
techniques can be used together in any combination to render a high-quality image.