.. _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. Members ------- 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. Note that this is separate from the fragment shader input attributes CONSTANT, LINEAR and PERSPECTIVE. We need the flatshade state at clipping time to determine how to set the color of new vertices. Also note that the draw module 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. light_twoside If set, there are per-vertex back-facing colors. The draw module 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 drawinga 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. point_sprite Whether points are drawn as sprites (textured quads). This is mutually exclusive with point_smooth. Note that sprite_coord_mode set to PIPE_SPRITE_COORD_NONE for all coords and point_sprite enabled is basically equivalent to point_sprite disabled. sprite_coord_mode Specifies how the value for each shader output should be computed when drawing sprites. If PIPE_SPRITE_COORD_NONE, don't change the vertex shader output. Otherwise, the four vertices of the resulting quad will be assigned texture coordinates. For PIPE_SPRITE_COORD_LOWER_LEFT, the lower left vertex will have coordinate (0,0,0,1). For PIPE_SPRITE_COORD_UPPER_LEFT, the upper-left vertex will have coordinate (0,0,0,1). This state is needed by the 'draw' module because that's where each point vertex is converted into four quad vertices. There's no other place to emit the new vertex texture coordinates which are required for sprite rendering. Note that when geometry shaders are available, this state could be removed. A special geometry shader defined by the state tracker could convert the incoming points into quads with the proper texture coords. scissor Whether the scissor test is enabled. multisample Whether :ref:`MSAA` is enabled. bypass_vs_clip_and_viewport Whether the entire TCL pipeline should be bypassed. This implies that vertices are pre-transformed for the viewport, and will not be run through the vertex shader. Note that implementations may still clip away vertices that are not in the viewport. 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. Notes ----- flatshade ^^^^^^^^^ The actual interpolated shading algorithm is obviously implementation-dependent, but will usually be Gourard for most hardware. bypass_vs_clip_and_viewport ^^^^^^^^^^^^^^^^^^^^^^^^^^^ When set, this implies that vertices are pre-transformed for the viewport, and will not be run through the vertex shader. Note that implementations may still clip away vertices that are not visible. flatshade_first ^^^^^^^^^^^^^^^ 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.