Graphics Reference
In-Depth Information
color buffer could be set such that no red values are written into the color
buffer. In addition, OpenGL ES 3.0 provides an interface to read back the
pixels from the framebuffer.
Note:
Alpha test and LogicOp are no longer part of the per-fragment
operations stage. These two stages exist in OpenGL 2.0 and
OpenGL ES 1.x. The alpha test stage is no longer needed because
the fragment shader can discard fragments; thus the alpha test
can be performed in the fragment shader. In addition, LogicOp
was removed because it is used only rarely by applications, and
the OpenGL ES working group did not receive requests from
independent software vendors (ISVs) to support this feature in
OpenGL ES 2.0.
OpenGL ES 2.0 ushered in the era of programmable shaders for handheld
devices and has been wildly successful in powering games, applications,
and user interfaces across a wide range of devices. OpenGL ES 3.0
extends OpenGL ES 2.0 to support many new rendering techniques,
optimizations, and visual quality enhancements. The following sections
provide a categorized overview of the major new features that have been
added to OpenGL ES 3.0. Each of these features will be described in detail
later in the topic.
OpenGL ES 3.0 introduces many new features related to texturing:
• sRGB textures and framebuffers—Allow the application to perform
gamma-correct rendering. Textures can be stored in gamma-corrected
sRGB space, uncorrected to linear space upon being fetched in the
shader, and then converted back to sRGB gamma-corrected space on
output to the framebuffer. This enables potentially higher visual fidelity
by properly computing lighting and other calculations in linear space.
• 2D texture arrays—A texture target that stores an array of 2D textures.
Such arrays might, for example, be used to perform texture animation.
Prior to 2D texture arrays, such animation was typically done by tiling
the frames of an animation in a single 2D texture and modifying the
texture coordinates to change animation frames. With 2D texture
arrays, each frame of the animation can be specified in a 2D slice of
the array.
