.. _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. Points ------ sprite_coord_enable ^^^^^^^^^^^^^^^^^^^ Specifies if a texture unit has its texture coordinates replaced or not. This is a packed bitfield containing the enable for all texcoords -- if all bits are zero, point sprites are effectively disabled. If any bit is set, then point_smooth and point_quad_rasterization are ignored; point smoothing is disabled and points are always rasterized as quads. If enabled, the four vertices of the resulting quad will be assigned texture coordinates, according to sprite_coord_mode. 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. .. note:: When geometry shaders are available, a special geometry shader could be used instead of this functionality, to convert incoming points into quads with the proper texture coordinates. point_quad_rasterization ^^^^^^^^^^^^^^^^^^^^^^^^ Determines if points should be rasterized as quads or points. Certain APIs, like Direct3D, always use quad rasterization 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. Other Members ^^^^^^^^^^^^^ light_twoside If set, there are per-vertex back-facing colors. :ref:`Draw` uses this state along with the front/back information to set the final vertex colors prior to rasterization. front_winding Indicates the window order of front-facing polygons, either PIPE_WINDING_CW or PIPE_WINDING_CCW cull_mode Indicates which polygons to cull, either PIPE_WINDING_NONE (cull no polygons), PIPE_WINDING_CW (cull clockwise-winding polygons), PIPE_WINDING_CCW (cull counter clockwise-winding polygons), or PIPE_WINDING_BOTH (cull all polygons). fill_cw Indicates how to fill clockwise polygons, either PIPE_POLYGON_MODE_FILL, PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT. fill_ccw Indicates how to fill counter clockwise 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_cw If set, clockwise polygons will have polygon offset factors applied offset_ccw If set, counter clockwise polygons will have polygon offset factors applied offset_units Specifies the polygon offset bias offset_scale Specifies the polygon offset scale 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. point_smooth Whether points should be smoothed. Point smoothing turns rectangular points into circles or ovals. point_size_per_vertex Whether vertices have a point size element. point_size The size of points, if not specified per-vertex. 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.