Graphics Reference
In-Depth Information
As you might have noticed, there isn't a stage named “multisampling.”
Multisampling is an anti-aliasing technique that duplicates operations
at a subfragment level. We describe how multisampling affects fragment
processing in more depth later in the chapter.
The chapter concludes with a discussion of methods for reading pixels
from and writing pixels to the framebuffer.
OpenGL ES supports three types of buffers, each of which stores different
data for every pixel in the framebuffer:
• Color buffer (composed of front and back color buffers)
• Depth buffer
• Stencil buffer
The size of a buffer—commonly referred to as the “depth of the buffer”
(but not to be confused with the depth buffer)—is measured by the
number of bits that are available for storing information for a single pixel.
The color buffer, for example, will have three components for storing the
red, green, and blue color components, and optional storage for the alpha
component. The depth of the color buffer is the sum of the number of bits
for all of its components. For the depth and stencil buffers, in contrast,
a single value represents the bit depth of a pixel in those buffers. For
example, a depth buffer might have 16 bits per pixel. The overall size of
the buffer is the sum of the bit depths of all of the components. Common
framebuffer depths include 16-bit RGB buffers, with 5 bits for red and
blue, and 6 bits for green (the human visual system is more sensitive to
green than to red or blue), and 32 bits divided equally for an RGBA buffer.
Additionally, the color buffer may be double buffered, such that
it contains two buffers: one that is displayed on the output device
(usually a monitor or LCD display), named the “front” buffer; and
another buffer that is hidden from the viewer, but used for constructing
the next image to be displayed, and called the “back” buffer. In double-
buffered applications, animation is accomplished by drawing into the
back buffer, and then swapping the front and back buffers to display
the new image. This swapping of buffers is usually synchronized with
the refresh cycle of the display device, which will give the illusion of
