src/gallium/docs/source/cso/blend.rst

   1 .. _blend:
   2
   3 Blend
   4 =====
   5
   6 This state controls blending of the final fragments into the target rendering
   7 buffers.
   8
   9 Blend Factors
  10 -------------
  11
  12 The blend factors largely follow the same pattern as their counterparts
  13 in other modern and legacy drawing APIs.
  14
  15 XXX blurb about dual-source blends
  16
  17 Logical Operations
  18 ------------------
  19
  20 Logical operations, also known as logicops, lops, or rops, are supported.
  21 Only two-operand logicops are available. When logicops are enabled, all other
  22 blend state is ignored, including per-render-target state, so logicops are
  23 performed on all render targets.
  24
  25 .. warning::
  26    The blend_enable flag is ignored for all render targets when logical
  27    operations are enabled.
  28
  29 For a source component `s` and destination component `d`, the logical
  30 operations are defined as taking the bits of each channel of each component,
  31 and performing one of the following operations per-channel:
  32
  33 * ``CLEAR``: 0
  34 * ``NOR``: :math:`\lnot(s \lor d)`
  35 * ``AND_INVERTED``: :math:`\lnot s \land d`
  36 * ``COPY_INVERTED``: :math:`\lnot s`
  37 * ``AND_REVERSE``: :math:`s \land \lnot d`
  38 * ``INVERT``: :math:`\lnot d`
  39 * ``XOR``: :math:`s \oplus d`
  40 * ``NAND``: :math:`\lnot(s \land d)`
  41 * ``AND``: :math:`s \land d`
  42 * ``EQUIV``: :math:`\lnot(s \oplus d)`
  43 * ``NOOP``: :math:`d`
  44 * ``OR_INVERTED``: :math:`\lnot s \lor d`
  45 * ``COPY``: :math:`s`
  46 * ``OR_REVERSE``: :math:`s \lor \lnot d`
  47 * ``OR``: :math:`s \lor d`
  48 * ``SET``: 1
  49
  50 .. note::
  51    The logical operation names and definitions match those of the OpenGL API,
  52    and are similar to the ROP2 and ROP3 definitions of GDI. This is
  53    intentional, to ease transitions to Gallium.
  54
  55 Members
  56 -------
  57
  58 These members affect all render targets.
  59
  60 dither
  61 %%%%%%
  62
  63 Whether dithering is enabled.
  64
  65 .. note::
  66    Dithering is completely implementation-dependent. It may be ignored by
  67    drivers for any reason, and some render targets may always or never be
  68    dithered depending on their format or usage flags.
  69
  70 logicop_enable
  71 %%%%%%%%%%%%%%
  72
  73 Whether the blender should perform a logicop instead of blending.
  74
  75 logicop_func
  76 %%%%%%%%%%%%
  77
  78 The logicop to use. One of ``PIPE_LOGICOP``.
  79
  80 independent_blend_enable
  81    If enabled, blend state is different for each render target, and
  82    for each render target set in the respective member of the rt array.
  83    If disabled, blend state is the same for all render targets, and only
  84    the first member of the rt array contains valid data.
  85 rt
  86    Contains the per-rendertarget blend state.
  87
  88 Per-rendertarget Members
  89 ------------------------
  90
  91 blend_enable
  92    If blending is enabled, perform a blend calculation according to blend
  93    functions and source/destination factors. Otherwise, the incoming fragment
  94    color gets passed unmodified (but colormask still applies).
  95 rgb_func
  96    The blend function to use for rgb channels. One of PIPE_BLEND.
  97 rgb_src_factor
  98    The blend source factor to use for rgb channels. One of PIPE_BLENDFACTOR.
  99 rgb_dst_factor
 100    The blend destination factor to use for rgb channels. One of PIPE_BLENDFACTOR.
 101 alpha_func
 102    The blend function to use for the alpha channel. One of PIPE_BLEND.
 103 alpha_src_factor
 104    The blend source factor to use for the alpha channel. One of PIPE_BLENDFACTOR.
 105 alpha_dst_factor
 106    The blend destination factor to use for alpha channel. One of PIPE_BLENDFACTOR.
 107 colormask
 108    Bitmask of which channels to write. Combination of PIPE_MASK bits.