2009-12-21 03:41:50 +00:00
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.. _rasterizer:
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2009-12-20 23:00:40 +00:00
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Rasterizer
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==========
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2010-01-06 16:42:53 +00:00
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The rasterizer state controls the rendering of points, lines and triangles.
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Attributes include polygon culling state, line width, line stipple,
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multisample state, scissoring and flat/smooth shading.
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2009-12-20 23:00:40 +00:00
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Members
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-------
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2009-12-21 01:25:36 +00:00
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flatshade
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If set, the provoking vertex of each polygon is used to determine the
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2010-01-06 16:42:53 +00:00
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color of the entire polygon. If not set, fragment colors will be
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interpolated between the vertex colors.
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Note that this is separate from the fragment shader input attributes
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CONSTANT, LINEAR and PERSPECTIVE. We need the flatshade state at
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clipping time to determine how to set the color of new vertices.
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Also note that the draw module can implement flat shading by copying
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the provoking vertex color to all the other vertices in the primitive.
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flatshade_first
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Whether the first vertex should be the provoking vertex, for most
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primitives. If not set, the last vertex is the provoking vertex.
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light_twoside
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If set, there are per-vertex back-facing colors. The draw module
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uses this state along with the front/back information to set the
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final vertex colors prior to rasterization.
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front_winding
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Indicates the window order of front-facing polygons, either
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PIPE_WINDING_CW or PIPE_WINDING_CCW
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cull_mode
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Indicates which polygons to cull, either PIPE_WINDING_NONE (cull no
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polygons), PIPE_WINDING_CW (cull clockwise-winding polygons),
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PIPE_WINDING_CCW (cull counter clockwise-winding polygons), or
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PIPE_WINDING_BOTH (cull all polygons).
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fill_cw
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Indicates how to fill clockwise polygons, either PIPE_POLYGON_MODE_FILL,
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PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT.
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fill_ccw
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Indicates how to fill counter clockwise polygons, either
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PIPE_POLYGON_MODE_FILL, PIPE_POLYGON_MODE_LINE or PIPE_POLYGON_MODE_POINT.
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2009-12-21 01:25:36 +00:00
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poly_stipple_enable
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Whether polygon stippling is enabled.
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2010-01-06 16:42:53 +00:00
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poly_smooth
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Controls OpenGL-style polygon smoothing/antialiasing
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offset_cw
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If set, clockwise polygons will have polygon offset factors applied
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offset_ccw
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If set, counter clockwise polygons will have polygon offset factors applied
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offset_units
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Specifies the polygon offset bias
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offset_scale
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Specifies the polygon offset scale
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line_width
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The width of lines.
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line_smooth
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Whether lines should be smoothed. Line smoothing is simply anti-aliasing.
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line_stipple_enable
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Whether line stippling is enabled.
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line_stipple_pattern
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16-bit bitfield of on/off flags, used to pattern the line stipple.
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line_stipple_factor
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When drawinga stippled line, each bit in the stipple pattern is
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repeated N times, where N = line_stipple_factor + 1.
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line_last_pixel
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Controls whether the last pixel in a line is drawn or not. OpenGL
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omits the last pixel to avoid double-drawing pixels at the ends of lines
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when drawing connected lines.
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2009-12-21 01:25:36 +00:00
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point_smooth
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Whether points should be smoothed. Point smoothing turns rectangular
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points into circles or ovals.
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point_size_per_vertex
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Whether vertices have a point size element.
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2010-01-06 16:42:53 +00:00
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point_size
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The size of points, if not specified per-vertex.
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point_size_min
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The minimum size of points.
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point_size_max
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The maximum size of points.
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point_sprite
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Whether points are drawn as sprites (textured quads)
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sprite_coord_mode
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Specifies how the value for each shader output should be computed when
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drawing sprites. If PIPE_SPRITE_COORD_NONE, don't change the vertex
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shader output. Otherwise, the four vertices of the resulting quad will
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be assigned texture coordinates. For PIPE_SPRITE_COORD_LOWER_LEFT, the
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lower left vertex will have coordinate (0,0,0,1).
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For PIPE_SPRITE_COORD_UPPER_LEFT, the upper-left vertex will have
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coordinate (0,0,0,1).
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This state is needed by the 'draw' module because that's where each
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point vertex is converted into four quad vertices. There's no other
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place to emit the new vertex texture coordinates which are required for
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sprite rendering.
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Note that when geometry shaders are available, this state could be
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removed. A special geometry shader defined by the state tracker could
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converts the incoming points into quads with the proper texture coords.
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scissor
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Whether the scissor test is enabled.
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2009-12-21 01:25:36 +00:00
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multisample
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2010-01-19 00:40:39 +00:00
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Whether :term:`MSAA` is enabled.
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2010-01-06 16:42:53 +00:00
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2009-12-21 01:25:36 +00:00
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bypass_vs_clip_and_viewport
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Whether the entire TCL pipeline should be bypassed. This implies that
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vertices are pre-transformed for the viewport, and will not be run
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through the vertex shader. Note that implementations may still clip away
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vertices that are not in the viewport.
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2010-01-06 16:42:53 +00:00
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2009-12-21 01:25:36 +00:00
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gl_rasterization_rules
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Whether the rasterizer should use (0.5, 0.5) pixel centers. When not set,
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the rasterizer will use (0, 0) for pixel centers.
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2010-01-06 16:42:53 +00:00
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2009-12-21 01:25:36 +00:00
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Notes
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-----
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flatshade
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^^^^^^^^^
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The actual interpolated shading algorithm is obviously
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implementation-dependent, but will usually be Gourard for most hardware.
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bypass_vs_clip_and_viewport
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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When set, this implies that vertices are pre-transformed for the viewport, and
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will not be run through the vertex shader. Note that implementations may still
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clip away vertices that are not visible.
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flatshade_first
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^^^^^^^^^^^^^^^
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There are several important exceptions to the specification of this rule.
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2009-12-21 04:37:40 +00:00
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* ``PIPE_PRIMITIVE_POLYGON``: The provoking vertex is always the first
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vertex. If the caller wishes to change the provoking vertex, they merely
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need to rotate the vertices themselves.
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* ``PIPE_PRIMITIVE_QUAD``, ``PIPE_PRIMITIVE_QUAD_STRIP``: This option has no
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effect; the provoking vertex is always the last vertex.
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* ``PIPE_PRIMITIVE_TRIANGLE_FAN``: When set, the provoking vertex is the
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second vertex, not the first. This permits each segment of the fan to have
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a different color.
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