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

   1 .. _rasterizer:
   2
   3 Rasterizer
   4 ==========
   5
   6 The rasterizer state controls the rendering of points, lines and triangles.
   7 Attributes include polygon culling state, line width, line stipple,
   8 multisample state, scissoring and flat/smooth shading.
   9
  10
  11 Members
  12 -------
  13
  14 flatshade
  15     If set, the provoking vertex of each polygon is used to determine the
  16     color of the entire polygon.  If not set, fragment colors will be
  17     interpolated between the vertex colors.
  18     Note that this is separate from the fragment shader input attributes
  19     CONSTANT, LINEAR and PERSPECTIVE.  We need the flatshade state at
  20     clipping time to determine how to set the color of new vertices.
  21     Also note that the draw module can implement flat shading by copying
  22     the provoking vertex color to all the other vertices in the primitive.
  23
  24 flatshade_first
  25     Whether the first vertex should be the provoking vertex, for most
  26     primitives. If not set, the last vertex is the provoking vertex.
  27
  28 light_twoside
  29     If set, there are per-vertex back-facing colors.  The draw module
  30     uses this state along with the front/back information to set the
  31     final vertex colors prior to rasterization.
  32
  33 front_winding
  34     Indicates the window order of front-facing polygons, either
  35     PIPE_WINDING_CW or PIPE_WINDING_CCW
  36 cull_mode
  37     Indicates which polygons to cull, either PIPE_WINDING_NONE (cull no
  38     polygons), PIPE_WINDING_CW (cull clockwise-winding polygons),
  39     PIPE_WINDING_CCW (cull counter clockwise-winding polygons), or
  40     PIPE_WINDING_BOTH (cull all polygons).
  41
  42 fill_cw
  43     Indicates how to fill clockwise polygons, either PIPE_POLYGON_MODE_FILL,
  44     PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT.
  45 fill_ccw
  46     Indicates how to fill counter clockwise polygons, either
  47     PIPE_POLYGON_MODE_FILL, PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT.
  48
  49 poly_stipple_enable
  50     Whether polygon stippling is enabled.
  51 poly_smooth
  52     Controls OpenGL-style polygon smoothing/antialiasing
  53 offset_cw
  54     If set, clockwise polygons will have polygon offset factors applied
  55 offset_ccw
  56     If set, counter clockwise polygons will have polygon offset factors applied
  57 offset_units
  58     Specifies the polygon offset bias
  59 offset_scale
  60     Specifies the polygon offset scale
  61
  62 line_width
  63     The width of lines.
  64 line_smooth
  65     Whether lines should be smoothed. Line smoothing is simply anti-aliasing.
  66 line_stipple_enable
  67     Whether line stippling is enabled.
  68 line_stipple_pattern
  69     16-bit bitfield of on/off flags, used to pattern the line stipple.
  70 line_stipple_factor
  71     When drawinga stippled line, each bit in the stipple pattern is
  72     repeated N times, where N = line_stipple_factor + 1.
  73 line_last_pixel
  74     Controls whether the last pixel in a line is drawn or not.  OpenGL
  75     omits the last pixel to avoid double-drawing pixels at the ends of lines
  76     when drawing connected lines.
  77
  78 point_smooth
  79     Whether points should be smoothed. Point smoothing turns rectangular
  80     points into circles or ovals.
  81 point_size_per_vertex
  82     Whether vertices have a point size element.
  83 point_size
  84     The size of points, if not specified per-vertex.
  85 point_sprite
  86     Whether points are drawn as sprites (textured quads)
  87 sprite_coord_mode
  88     Specifies how the value for each shader output should be computed when
  89     drawing sprites.  If PIPE_SPRITE_COORD_NONE, don't change the vertex
  90     shader output.  Otherwise, the four vertices of the resulting quad will
  91     be assigned texture coordinates.  For PIPE_SPRITE_COORD_LOWER_LEFT, the
  92     lower left vertex will have coordinate (0,0,0,1).
  93     For PIPE_SPRITE_COORD_UPPER_LEFT, the upper-left vertex will have
  94     coordinate (0,0,0,1).
  95     This state is needed by the 'draw' module because that's where each
  96     point vertex is converted into four quad vertices.  There's no other
  97     place to emit the new vertex texture coordinates which are required for
  98     sprite rendering.
  99     Note that when geometry shaders are available, this state could be
 100     removed.  A special geometry shader defined by the state tracker could
 101     converts the incoming points into quads with the proper texture coords.
 102
 103 scissor
 104     Whether the scissor test is enabled.
 105
 106 multisample
 107     Whether :ref:`MSAA` is enabled.
 108
 109 bypass_vs_clip_and_viewport
 110     Whether the entire TCL pipeline should be bypassed. This implies that
 111     vertices are pre-transformed for the viewport, and will not be run
 112     through the vertex shader. Note that implementations may still clip away
 113     vertices that are not in the viewport.
 114
 115 gl_rasterization_rules
 116     Whether the rasterizer should use (0.5, 0.5) pixel centers. When not set,
 117     the rasterizer will use (0, 0) for pixel centers.
 118
 119
 120 Notes
 121 -----
 122
 123 flatshade
 124 ^^^^^^^^^
 125
 126 The actual interpolated shading algorithm is obviously
 127 implementation-dependent, but will usually be Gourard for most hardware.
 128
 129 bypass_vs_clip_and_viewport
 130 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 131
 132 When set, this implies that vertices are pre-transformed for the viewport, and
 133 will not be run through the vertex shader. Note that implementations may still
 134 clip away vertices that are not visible.
 135
 136 flatshade_first
 137 ^^^^^^^^^^^^^^^
 138
 139 There are several important exceptions to the specification of this rule.
 140
 141 * ``PIPE_PRIMITIVE_POLYGON``: The provoking vertex is always the first
 142   vertex. If the caller wishes to change the provoking vertex, they merely
 143   need to rotate the vertices themselves.
 144 * ``PIPE_PRIMITIVE_QUAD``, ``PIPE_PRIMITIVE_QUAD_STRIP``: This option has no
 145   effect; the provoking vertex is always the last vertex.
 146 * ``PIPE_PRIMITIVE_TRIANGLE_FAN``: When set, the provoking vertex is the
 147   second vertex, not the first. This permits each segment of the fan to have
 148   a different color.