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.. _sampler:
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Sampler
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=======
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Texture units have many options for selecting texels from loaded textures;
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this state controls an individual texture unit's texel-sampling settings.
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Texture coordinates are always treated as four-dimensional, and referred to
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with the traditional (S, T, R, Q) notation.
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Members
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-------
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wrap_s
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    How to wrap the S coordinate. One of PIPE_TEX_WRAP_*.
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wrap_t
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    How to wrap the T coordinate. One of PIPE_TEX_WRAP_*.
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wrap_r
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    How to wrap the R coordinate. One of PIPE_TEX_WRAP_*.
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The wrap modes are:
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* ``PIPE_TEX_WRAP_REPEAT``: Standard coord repeat/wrap-around mode.
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* ``PIPE_TEX_WRAP_CLAMP_TO_EDGE``: Clamp coord to edge of texture, the border
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  color is never sampled.
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* ``PIPE_TEX_WRAP_CLAMP_TO_BORDER``: Clamp coord to border of texture, the
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  border color is sampled when coords go outside the range [0,1].
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* ``PIPE_TEX_WRAP_CLAMP``: The coord is clamped to the range [0,1] before
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  scaling to the texture size.  This corresponds to the legacy OpenGL GL_CLAMP
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  texture wrap mode.  Historically, this mode hasn't acted consistantly across
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  all graphics hardware.  It sometimes acts like CLAMP_TO_EDGE or
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  CLAMP_TO_BORDER.  The behaviour may also vary depending on linear vs.
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  nearest sampling mode.
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* ``PIPE_TEX_WRAP_MIRROR_REPEAT``: If the integer part of the coordinate
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  is odd, the coord becomes (1 - coord).  Then, normal texture REPEAT is
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  applied to the coord.
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* ``PIPE_TEX_WRAP_MIRROR_CLAMP_TO_EDGE``: First, the absolute value of the
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  coordinate is computed.  Then, regular CLAMP_TO_EDGE is applied to the coord.
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* ``PIPE_TEX_WRAP_MIRROR_CLAMP_TO_BORDER``: First, the absolute value of the
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  coordinate is computed.  Then, regular CLAMP_TO_BORDER is applied to the
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  coord.
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* ``PIPE_TEX_WRAP_MIRROR_CLAMP``: First, the absolute value of the coord is
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  computed.  Then, regular CLAMP is applied to the coord.
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min_img_filter
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    The image filter to use when minifying texels. One of PIPE_TEX_FILTER_*.
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mag_img_filter
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    The image filter to use when magnifying texels. One of PIPE_TEX_FILTER_*.
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The texture image filter modes are:
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* ``PIPE_TEX_FILTER_NEAREST``: One texel is fetched from the texture image
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  at the texture coordinate.
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* ``PIPE_TEX_FILTER_LINEAR``: Two, four or eight texels (depending on the
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  texture dimensions; 1D/2D/3D) are fetched from the texture image and
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  linearly weighted and blended together.
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min_mip_filter
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    The filter to use when minifying mipmapped textures. One of
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    PIPE_TEX_MIPFILTER_*.
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The texture mip filter modes are:
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* ``PIPE_TEX_MIPFILTER_NEAREST``: A single mipmap level/image is selected
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  according to the texture LOD (lambda) value.
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* ``PIPE_TEX_MIPFILTER_LINEAR``: The two mipmap levels/images above/below
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  the texture LOD value are sampled from.  The results of sampling from
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  those two images are blended together with linear interpolation.
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* ``PIPE_TEX_MIPFILTER_NONE``: Mipmap filtering is disabled.  All texels
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  are taken from the level 0 image.
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compare_mode
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    If set to PIPE_TEX_COMPARE_R_TO_TEXTURE, the result of texture sampling
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    is not a color but a true/false value which is the result of comparing the
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    sampled texture value (typically a Z value from a depth texture) to the
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    texture coordinate's R component.
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    If set to PIPE_TEX_COMPARE_NONE, no comparison calculation is performed.
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compare_func
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    The inequality operator used when compare_mode=1.  One of PIPE_FUNC_x.
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normalized_coords
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    If set, the incoming texture coordinates (nominally in the range [0,1])
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    will be scaled by the texture width, height, depth to compute texel
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    addresses.  Otherwise, the texture coords are used as-is (they are not
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    scaled by the texture dimensions).
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    When normalized_coords=0, only a subset of the texture wrap modes are
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    allowed: PIPE_TEX_WRAP_CLAMP, PIPE_TEX_WRAP_CLAMP_TO_EDGE and
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    PIPE_TEX_WRAP_CLAMP_TO_BORDER.
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lod_bias
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    Bias factor which is added to the computed level of detail.
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    The normal level of detail is computed from the partial derivatives of
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    the texture coordinates and/or the fragment shader TEX/TXB/TXL
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    instruction.
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min_lod
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    Minimum level of detail, used to clamp LOD after bias.  The LOD values
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    correspond to mipmap levels where LOD=0 is the level 0 mipmap image.
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max_lod
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    Maximum level of detail, used to clamp LOD after bias.
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border_color
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    Color union used for texel coordinates that are outside the [0,width-1],
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    [0, height-1] or [0, depth-1] ranges. Interpreted according to sampler
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    view format, unless the driver reports
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    PIPE_CAP_TEXTURE_BORDER_COLOR_QUIRK, in which case special care has to be
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    taken (see description of the cap).
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max_anisotropy
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    Maximum anistropy ratio to use when sampling from textures.  For example,
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    if max_anistropy=4, a region of up to 1 by 4 texels will be sampled.
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    Set to zero to disable anisotropic filtering.  Any other setting enables
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    anisotropic filtering, however it's not unexpected some drivers only will
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    change their filtering with a setting of 2 and higher.
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seamless_cube_map
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    If set, the bilinear filter of a cube map may take samples from adjacent
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    cube map faces when sampled near a texture border to produce a seamless
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    look.