Graphics Reference
In-Depth Information
GL_FUNC_REVERSE_SUBTRACT
operator reverses the blending equation,
such that the incoming fragment colors are subtracted from the current
pixel value.
void
glBlendEquation
(GLenum
mode
)
mode
specifies the blending operator. Valid values are
GL_FUNC_ADD
,
GL_FUNC_SUBTRACT
,
GL_FUNC_REVERSE_SUBTRACT
,
GL_MIN
, or
GL_MAX
.
void
glBlendEquationSeparate
(GLenum
modeRGB
,
GLenum
modeAlpha
)
modeRGB
specifies the blending operator for the red, green, and blue
components
modeAlpha
specifies the alpha component blending operator
On a system where the number of colors available in the framebuffer is
limited due to the number of bits per component in the framebuffer, we
can simulate greater color depth using dithering. Dithering algorithms
arrange colors in such a way that the image appears to have more
available colors than are really present. OpenGL ES 3.0 doesn't specify
which dithering algorithm is to be used in supporting its dithering stage;
the technique is very implementation dependent.
The only control your application has over dithering is whether it is
applied to the final pixels. This decision is entirely controlled by calling
glEnable
or
glDisable
with
GL_DITHER
to specify dithering's use in the
pipeline. Initially, dithering is enabled.
Anti-aliasing is an important technique for improving the quality of
generated images by trying to reduce the visual artifacts of rendering
into discrete pixels. The geometric primitives that OpenGL ES 3.0 renders
are rasterized onto a grid, and their edges may become deformed in that
