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_size_min
  86     The minimum size of points.
  87 point_size_max
  88     The maximum size of points.
  89 point_sprite
  90     Whether points are drawn as sprites (textured quads)
  91 sprite_coord_mode
  92     Specifies how the value for each shader output should be computed when
  93     drawing sprites.  If PIPE_SPRITE_COORD_NONE, don't change the vertex
  94     shader output.  Otherwise, the four vertices of the resulting quad will
  95     be assigned texture coordinates.  For PIPE_SPRITE_COORD_LOWER_LEFT, the
  96     lower left vertex will have coordinate (0,0,0,1).
  97     For PIPE_SPRITE_COORD_UPPER_LEFT, the upper-left vertex will have
  98     coordinate (0,0,0,1).
  99     This state is needed by the 'draw' module because that's where each
 100     point vertex is converted into four quad vertices.  There's no other
 101     place to emit the new vertex texture coordinates which are required for
 102     sprite rendering.
 103     Note that when geometry shaders are available, this state could be
 104     removed.  A special geometry shader defined by the state tracker could
 105     converts the incoming points into quads with the proper texture coords.
 106
 107 scissor
 108     Whether the scissor test is enabled.
 109
 110 multisample
 111     Whether :ref:`MSAA` is enabled.
 112
 113 bypass_vs_clip_and_viewport
 114     Whether the entire TCL pipeline should be bypassed. This implies that
 115     vertices are pre-transformed for the viewport, and will not be run
 116     through the vertex shader. Note that implementations may still clip away
 117     vertices that are not in the viewport.
 118
 119 gl_rasterization_rules
 120     Whether the rasterizer should use (0.5, 0.5) pixel centers. When not set,
 121     the rasterizer will use (0, 0) for pixel centers.
 122
 123
 124 Notes
 125 -----
 126
 127 flatshade
 128 ^^^^^^^^^
 129
 130 The actual interpolated shading algorithm is obviously
 131 implementation-dependent, but will usually be Gourard for most hardware.
 132
 133 bypass_vs_clip_and_viewport
 134 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 135
 136 When set, this implies that vertices are pre-transformed for the viewport, and
 137 will not be run through the vertex shader. Note that implementations may still
 138 clip away vertices that are not visible.
 139
 140 flatshade_first
 141 ^^^^^^^^^^^^^^^
 142
 143 There are several important exceptions to the specification of this rule.
 144
 145 * ``PIPE_PRIMITIVE_POLYGON``: The provoking vertex is always the first
 146   vertex. If the caller wishes to change the provoking vertex, they merely
 147   need to rotate the vertices themselves.
 148 * ``PIPE_PRIMITIVE_QUAD``, ``PIPE_PRIMITIVE_QUAD_STRIP``: This option has no
 149   effect; the provoking vertex is always the last vertex.
 150 * ``PIPE_PRIMITIVE_TRIANGLE_FAN``: When set, the provoking vertex is the
 151   second vertex, not the first. This permits each segment of the fan to have
 152   a different color.