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

   1 .. _sampler:
   2
   3 Sampler
   4 =======
   5
   6 Texture units have many options for selecting texels from loaded textures;
   7 this state controls an individual texture unit's texel-sampling settings.
   8
   9 Texture coordinates are always treated as four-dimensional, and referred to
  10 with the traditional (S, T, R, Q) notation.
  11
  12 Members
  13 -------
  14
  15 wrap_s
  16     How to wrap the S coordinate. One of PIPE_TEX_WRAP_*.
  17 wrap_t
  18     How to wrap the T coordinate. One of PIPE_TEX_WRAP_*.
  19 wrap_r
  20     How to wrap the R coordinate. One of PIPE_TEX_WRAP_*.
  21
  22 The wrap modes are:
  23
  24 * ``PIPE_TEX_WRAP_REPEAT``: Standard coord repeat/wrap-around mode.
  25 * ``PIPE_TEX_WRAP_CLAMP_TO_EDGE``: Clamp coord to edge of texture, the border
  26   color is never sampled.
  27 * ``PIPE_TEX_WRAP_CLAMP_TO_BORDER``: Clamp coord to border of texture, the
  28   border color is sampled when coords go outside the range [0,1].
  29 * ``PIPE_TEX_WRAP_CLAMP``: The coord is clamped to the range [0,1] before
  30   scaling to the texture size.  This corresponds to the legacy OpenGL GL_CLAMP
  31   texture wrap mode.  Historically, this mode hasn't acted consistantly across
  32   all graphics hardware.  It sometimes acts like CLAMP_TO_EDGE or
  33   CLAMP_TO_BORDER.  The behaviour may also vary depending on linear vs.
  34   nearest sampling mode.
  35 * ``PIPE_TEX_WRAP_MIRROR_REPEAT``: If the integer part of the coordinate
  36   is odd, the coord becomes (1 - coord).  Then, normal texture REPEAT is
  37   applied to the coord.
  38 * ``PIPE_TEX_WRAP_MIRROR_CLAMP_TO_EDGE``: First, the absolute value of the
  39   coordinate is computed.  Then, regular CLAMP_TO_EDGE is applied to the coord.
  40 * ``PIPE_TEX_WRAP_MIRROR_CLAMP_TO_BORDER``: First, the absolute value of the
  41   coordinate is computed.  Then, regular CLAMP_TO_BORDER is applied to the
  42   coord.
  43 * ``PIPE_TEX_WRAP_MIRROR_CLAMP``: First, the absolute value of the coord is
  44   computed.  Then, regular CLAMP is applied to the coord.
  45
  46
  47 min_img_filter
  48     The image filter to use when minifying texels. One of PIPE_TEX_FILTER_*.
  49 mag_img_filter
  50     The image filter to use when magnifying texels. One of PIPE_TEX_FILTER_*.
  51
  52 The texture image filter modes are:
  53
  54 * ``PIPE_TEX_FILTER_NEAREST``: One texel is fetched from the texture image
  55   at the texture coordinate.
  56 * ``PIPE_TEX_FILTER_LINEAR``: Two, four or eight texels (depending on the
  57   texture dimensions; 1D/2D/3D) are fetched from the texture image and
  58   linearly weighted and blended together.
  59
  60 min_mip_filter
  61     The filter to use when minifying mipmapped textures. One of
  62     PIPE_TEX_MIPFILTER_*.
  63
  64 The texture mip filter modes are:
  65
  66 * ``PIPE_TEX_MIPFILTER_NEAREST``: A single mipmap level/image is selected
  67   according to the texture LOD (lambda) value.
  68 * ``PIPE_TEX_MIPFILTER_LINEAR``: The two mipmap levels/images above/below
  69   the texture LOD value are sampled from.  The results of sampling from
  70   those two images are blended together with linear interpolation.
  71 * ``PIPE_TEX_MIPFILTER_NONE``: Mipmap filtering is disabled.  All texels
  72   are taken from the level 0 image.
  73
  74
  75 compare_mode
  76     If set to PIPE_TEX_COMPARE_R_TO_TEXTURE, the result of texture sampling
  77     is not a color but a true/false value which is the result of comparing the
  78     sampled texture value (typically a Z value from a depth texture) to the
  79     texture coordinate's R component.
  80     If set to PIPE_TEX_COMPARE_NONE, no comparison calculation is performed.
  81 compare_func
  82     The inequality operator used when compare_mode=1.  One of PIPE_FUNC_x.
  83 normalized_coords
  84     If set, the incoming texture coordinates (nominally in the range [0,1])
  85     will be scaled by the texture width, height, depth to compute texel
  86     addresses.  Otherwise, the texture coords are used as-is (they are not
  87     scaled by the texture dimensions).
  88 lod_bias
  89     Bias factor which is added to the computed level of detail.
  90     The normal level of detail is computed from the partial derivatives of
  91     the texture coordinates and/or the fragment shader TEX/TXB/TXL
  92     instruction.
  93 min_lod
  94     Minimum level of detail, used to clamp LOD after bias.  The LOD values
  95     correspond to mipmap levels where LOD=0 is the level 0 mipmap image.
  96 max_lod
  97     Maximum level of detail, used to clamp LOD after bias.
  98 border_color
  99     RGBA color used for texel coordinates that are outside the [0,width-1],
 100     [0, height-1] or [0, depth-1] ranges.
 101 max_anisotropy
 102     Maximum anistropy ratio to use when sampling from textures.  For example,
 103     if max_anistropy=4, a region of up to 1 by 4 texels will be sampled.
 104     Set to zero to disable anisotropic filtering.  Any other setting enables
 105     anisotropic filtering, however it's not unexpected some drivers only will
 106     change their filtering with a setting of 2 and higher.