From 54ddf642dfaea3532b60c8239cb6a83950762e43 Mon Sep 17 00:00:00 2001 From: Corbin Simpson Date: Wed, 23 Dec 2009 23:36:06 -0800 Subject: docs: Add all semantics to TGSI doc, regen. --- src/gallium/docs/source/tgsi.rst | 91 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 86 insertions(+), 5 deletions(-) (limited to 'src/gallium/docs/source') diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst index 86c09046f7..12687f29dc 100644 --- a/src/gallium/docs/source/tgsi.rst +++ b/src/gallium/docs/source/tgsi.rst @@ -1180,11 +1180,92 @@ Declaration Semantic The meanings of the individual semantic names are explained in the following sections. +TGSI_SEMANTIC_POSITION +"""""""""""""""""""""" -FACE -"""" +Position, sometimes known as HPOS or WPOS for historical reasons, is the +location of the vertex in space, in ``(x, y, z, w)`` format. ``x``, ``y``, and ``z`` +are the Cartesian coordinates, and ``w`` is the homogenous coordinate and used +for the perspective divide, if enabled. - Valid only in a fragment shader INPUT declaration. +As a vertex shader output, position should be scaled to the viewport. When +used in fragment shaders, position will --- - FACE.x is negative when the primitive is back facing. FACE.x is positive - when the primitive is front facing. +XXX --- wait a minute. Should position be in [0,1] for x and y? + +XXX additionally, is there a way to configure the perspective divide? it's +accelerated on most chipsets AFAIK... + +Position, if not specified, usually defaults to ``(0, 0, 0, 1)``, and can +be partially specified as ``(x, y, 0, 1)`` or ``(x, y, z, 1)``. + +XXX usually? can we solidify that? + +TGSI_SEMANTIC_COLOR +""""""""""""""""""" + +Colors are used to, well, color the primitives. Colors are always in +``(r, g, b, a)`` format. + +If alpha is not specified, it defaults to 1. + +TGSI_SEMANTIC_BCOLOR +"""""""""""""""""""" + +Back-facing colors are only used for back-facing polygons, and are only valid +in vertex shader outputs. After rasterization, all polygons are front-facing +and COLOR and BCOLOR end up occupying the same slots in the fragment, so +all BCOLORs effectively become regular COLORs in the fragment shader. + +TGSI_SEMANTIC_FOG +""""""""""""""""" + +The fog coordinate historically has been used to replace the depth coordinate +for generation of fog in dedicated fog blocks. Gallium, however, does not use +dedicated fog acceleration, placing it entirely in the fragment shader +instead. + +The fog coordinate should be written in ``(f, 0, 0, 1)`` format. Only the first +component matters when writing from the vertex shader; the driver will ensure +that the coordinate is in this format when used as a fragment shader input. + +TGSI_SEMANTIC_PSIZE +""""""""""""""""""" + +PSIZE, or point size, is used to specify point sizes per-vertex. It should +be in ``(p, n, x, f)`` format, where ``p`` is the point size, ``n`` is the minimum +size, ``x`` is the maximum size, and ``f`` is the fade threshold. + +XXX this is arb_vp. is this what we actually do? should double-check... + +When using this semantic, be sure to set the appropriate state in the +:ref:`rasterizer` first. + +TGSI_SEMANTIC_GENERIC +""""""""""""""""""""" + +Generic semantics are nearly always used for texture coordinate attributes, +in ``(s, t, r, q)`` format. ``t`` and ``r`` may be unused for certain kinds +of lookups, and ``q`` is the level-of-detail bias for biased sampling. + +These attributes are called "generic" because they may be used for anything +else, including parameters, texture generation information, or anything that +can be stored inside a four-component vector. + +TGSI_SEMANTIC_NORMAL +"""""""""""""""""""" + +XXX no clue. + +TGSI_SEMANTIC_FACE +"""""""""""""""""" + +FACE is the facing bit, to store the facing information for the fragment +shader. ``(f, 0, 0, 1)`` is the format. The first component will be positive +when the fragment is front-facing, and negative when the component is +back-facing. + +TGSI_SEMANTIC_EDGEFLAG +"""""""""""""""""""""" + +XXX no clue -- cgit v1.2.3