.. _rasterizer: Rasterizer ========== The rasterizer state controls the rendering of points, lines and triangles. Attributes include polygon culling state, line width, line stipple, multisample state, scissoring and flat/smooth shading. Shading ------- flatshade ^^^^^^^^^ If set, the provoking vertex of each polygon is used to determine the color of the entire polygon. If not set, fragment colors will be interpolated between the vertex colors. The actual interpolated shading algorithm is obviously implementation-dependent, but will usually be Gourard for most hardware. .. note:: This is separate from the fragment shader input attributes CONSTANT, LINEAR and PERSPECTIVE. The flatshade state is needed at clipping time to determine how to set the color of new vertices. :ref:`Draw` can implement flat shading by copying the provoking vertex color to all the other vertices in the primitive. flatshade_first ^^^^^^^^^^^^^^^ Whether the first vertex should be the provoking vertex, for most primitives. If not set, the last vertex is the provoking vertex. There are several important exceptions to the specification of this rule. * ``PIPE_PRIMITIVE_POLYGON``: The provoking vertex is always the first vertex. If the caller wishes to change the provoking vertex, they merely need to rotate the vertices themselves. * ``PIPE_PRIMITIVE_QUAD``, ``PIPE_PRIMITIVE_QUAD_STRIP``: This option has no effect; the provoking vertex is always the last vertex. * ``PIPE_PRIMITIVE_TRIANGLE_FAN``: When set, the provoking vertex is the second vertex, not the first. This permits each segment of the fan to have a different color. Polygons -------- light_twoside ^^^^^^^^^^^^^ If set, there are per-vertex back-facing colors. The hardware (perhaps assisted by :ref:`Draw`) should be set up to use this state along with the front/back information to set the final vertex colors prior to rasterization. The frontface vertex shader color output is marked with TGSI semantic COLOR[0], and backface COLOR[1]. front_ccw Indicates whether the window order of front-facing polygons is counter-clockwise (TRUE) or clockwise (FALSE). cull_mode Indicates which faces of polygons to cull, either PIPE_FACE_NONE (cull no polygons), PIPE_FACE_FRONT (cull front-facing polygons), PIPE_FACE_BACK (cull back-facing polygons), or PIPE_FACE_FRONT_AND_BACK (cull all polygons). fill_front Indicates how to fill front-facing polygons, either PIPE_POLYGON_MODE_FILL, PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT. fill_back Indicates how to fill back-facing polygons, either PIPE_POLYGON_MODE_FILL, PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT. poly_stipple_enable Whether polygon stippling is enabled. poly_smooth Controls OpenGL-style polygon smoothing/antialiasing offset_point If set, point-filled polygons will have polygon offset factors applied offset_line If set, line-filled polygons will have polygon offset factors applied offset_tri If set, filled polygons will have polygon offset factors applied offset_units Specifies the polygon offset bias offset_scale Specifies the polygon offset scale Lines ----- line_width The width of lines. line_smooth Whether lines should be smoothed. Line smoothing is simply anti-aliasing. line_stipple_enable Whether line stippling is enabled. line_stipple_pattern 16-bit bitfield of on/off flags, used to pattern the line stipple. line_stipple_factor When drawing a stippled line, each bit in the stipple pattern is repeated N times, where N = line_stipple_factor + 1. line_last_pixel Controls whether the last pixel in a line is drawn or not. OpenGL omits the last pixel to avoid double-drawing pixels at the ends of lines when drawing connected lines. Points ------ sprite_coord_enable ^^^^^^^^^^^^^^^^^^^ Controls automatic texture coordinate generation for rendering sprite points. When bit k in the sprite_coord_enable bitfield is set, then generic input k to the fragment shader will get an automatically computed texture coordinate. The texture coordinate will be of the form (s, t, 0, 1) where s varies from 0 to 1 from left to right while t varies from 0 to 1 according to the state of 'sprite_coord_mode' (see below). If any bit is set, then point_smooth MUST be disabled (there are no round sprites) and point_quad_rasterization MUST be true (sprites are always rasterized as quads). Any mismatch between these states should be considered a bug in the state-tracker. This feature is implemented in the :ref:`Draw` module but may also be implemented natively by GPUs or implemented with a geometry shader. sprite_coord_mode ^^^^^^^^^^^^^^^^^ Specifies how the value for each shader output should be computed when drawing point sprites. For PIPE_SPRITE_COORD_LOWER_LEFT, the lower-left vertex will have coordinates (0,0,0,1). For PIPE_SPRITE_COORD_UPPER_LEFT, the upper-left vertex will have coordinates (0,0,0,1). This state is used by :ref:`Draw` to generate texcoords. point_quad_rasterization ^^^^^^^^^^^^^^^^^^^^^^^^ Determines if points should be rasterized according to quad or point rasterization rules. OpenGL actually has quite different rasterization rules for points and point sprites - hence this indicates if points should be rasterized as points or according to point sprite (which decomposes them into quads, basically) rules. Additionally Direct3D will always use quad rasterization rules for points, regardless of whether point sprites are enabled or not. If this state is enabled, point smoothing and antialiasing are disabled. If it is disabled, point sprite coordinates are not generated. .. note:: Some renderers always internally translate points into quads; this state still affects those renderers by overriding other rasterization state. point_smooth Whether points should be smoothed. Point smoothing turns rectangular points into circles or ovals. point_size_per_vertex Whether the vertex shader is expected to have a point size output. Undefined behaviour is permitted if there is disagreement between this flag and the actual bound shader. point_size The size of points, if not specified per-vertex. Other Members ------------- scissor Whether the scissor test is enabled. multisample Whether :term:`MSAA` is enabled. gl_rasterization_rules Whether the rasterizer should use (0.5, 0.5) pixel centers. When not set, the rasterizer will use (0, 0) for pixel centers.