2 * Mesa 3-D graphics library
5 * Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
7 * Permission is hereby granted, free of charge, to any person obtaining a
8 * copy of this software and associated documentation files (the "Software"),
9 * to deal in the Software without restriction, including without limitation
10 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
11 * and/or sell copies of the Software, and to permit persons to whom the
12 * Software is furnished to do so, subject to the following conditions:
14 * The above copyright notice and this permission notice shall be included
15 * in all copies or substantial portions of the Software.
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
18 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
21 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
22 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
26 * Triangle Rasterizer Template
28 * This file is #include'd to generate custom triangle rasterizers.
30 * The following macros may be defined to indicate what auxillary information
31 * must be interpolated across the triangle:
32 * INTERP_Z - if defined, interpolate integer Z values
33 * INTERP_RGB - if defined, interpolate integer RGB values
34 * INTERP_ALPHA - if defined, interpolate integer Alpha values
35 * INTERP_INDEX - if defined, interpolate color index values
36 * INTERP_INT_TEX - if defined, interpolate integer ST texcoords
37 * (fast, simple 2-D texture mapping, without
38 * perspective correction)
39 * INTERP_ATTRIBS - if defined, interpolate arbitrary attribs (texcoords,
40 * varying vars, etc) This also causes W to be
41 * computed for perspective correction).
43 * When one can directly address pixels in the color buffer the following
44 * macros can be defined and used to compute pixel addresses during
45 * rasterization (see pRow):
46 * PIXEL_TYPE - the datatype of a pixel (GLubyte, GLushort, GLuint)
47 * BYTES_PER_ROW - number of bytes per row in the color buffer
48 * PIXEL_ADDRESS(X,Y) - returns the address of pixel at (X,Y) where
49 * Y==0 at bottom of screen and increases upward.
51 * Similarly, for direct depth buffer access, this type is used for depth
52 * buffer addressing (see zRow):
53 * DEPTH_TYPE - either GLushort or GLuint
55 * Optionally, one may provide one-time setup code per triangle:
56 * SETUP_CODE - code which is to be executed once per triangle
58 * The following macro MUST be defined:
59 * RENDER_SPAN(span) - code to write a span of pixels.
61 * This code was designed for the origin to be in the lower-left corner.
63 * Inspired by triangle rasterizer code written by Allen Akin. Thanks Allen!
66 * Some notes on rasterization accuracy:
68 * This code uses fixed point arithmetic (the GLfixed type) to iterate
69 * over the triangle edges and interpolate ancillary data (such as Z,
70 * color, secondary color, etc). The number of fractional bits in
71 * GLfixed and the value of SUB_PIXEL_BITS has a direct bearing on the
72 * accuracy of rasterization.
74 * If SUB_PIXEL_BITS=4 then we'll snap the vertices to the nearest
75 * 1/16 of a pixel. If we're walking up a long, nearly vertical edge
76 * (dx=1/16, dy=1024) we'll need 4 + 10 = 14 fractional bits in
77 * GLfixed to walk the edge without error. If the maximum viewport
78 * height is 4K pixels, then we'll need 4 + 12 = 16 fractional bits.
80 * Historically, Mesa has used 11 fractional bits in GLfixed, snaps
81 * vertices to 1/16 pixel and allowed a maximum viewport height of 2K
82 * pixels. 11 fractional bits is actually insufficient for accurately
83 * rasterizing some triangles. More recently, the maximum viewport
84 * height was increased to 4K pixels. Thus, Mesa should be using 16
85 * fractional bits in GLfixed. Unfortunately, there may be some issues
86 * with setting FIXED_FRAC_BITS=16, such as multiplication overflow.
87 * This will have to be examined in some detail...
89 * For now, if you find rasterization errors, particularly with tall,
90 * sliver triangles, try increasing FIXED_FRAC_BITS and/or decreasing
96 * Some code we unfortunately need to prevent negative interpolated colors.
98 #ifndef CLAMP_INTERPOLANT
99 #define CLAMP_INTERPOLANT(CHANNEL, CHANNELSTEP, LEN) \
101 GLfixed endVal = span.CHANNEL + (LEN) * span.CHANNELSTEP; \
103 span.CHANNEL -= endVal; \
105 if (span.CHANNEL < 0) { \
112 static void NAME(GLcontext
*ctx
, const SWvertex
*v0
,
117 const SWvertex
*v0
, *v1
; /* Y(v0) < Y(v1) */
118 GLfloat dx
; /* X(v1) - X(v0) */
119 GLfloat dy
; /* Y(v1) - Y(v0) */
120 GLfloat dxdy
; /* dx/dy */
121 GLfixed fdxdy
; /* dx/dy in fixed-point */
122 GLfloat adjy
; /* adjust from v[0]->fy to fsy, scaled */
123 GLfixed fsx
; /* first sample point x coord */
125 GLfixed fx0
; /* fixed pt X of lower endpoint */
126 GLint lines
; /* number of lines to be sampled on this edge */
129 const SWcontext
*swrast
= SWRAST_CONTEXT(ctx
);
131 const GLint depthBits
= ctx
->DrawBuffer
->Visual
.depthBits
;
132 const GLint fixedToDepthShift
= depthBits
<= 16 ? FIXED_SHIFT
: 0;
133 const GLfloat maxDepth
= ctx
->DrawBuffer
->_DepthMaxF
;
134 #define FixedToDepth(F) ((F) >> fixedToDepthShift)
136 EdgeT eMaj
, eTop
, eBot
;
138 const SWvertex
*vMin
, *vMid
, *vMax
; /* Y(vMin)<=Y(vMid)<=Y(vMax) */
139 GLfloat bf
= SWRAST_CONTEXT(ctx
)->_BackfaceSign
;
140 const GLint snapMask
= ~((FIXED_ONE
/ (1 << SUB_PIXEL_BITS
)) - 1); /* for x/y coord snapping */
141 GLfixed vMin_fx
, vMin_fy
, vMid_fx
, vMid_fy
, vMax_fx
, vMax_fy
;
147 INIT_SPAN(span
, GL_POLYGON
);
148 span
.y
= 0; /* silence warnings */
151 (void) fixedToDepthShift
;
155 printf("%s()\n", __FUNCTION__);
156 printf(" %g, %g, %g\n",
157 v0->attrib[FRAG_ATTRIB_WPOS][0],
158 v0->attrib[FRAG_ATTRIB_WPOS][1],
159 v0->attrib[FRAG_ATTRIB_WPOS][2]);
160 printf(" %g, %g, %g\n",
161 v1->attrib[FRAG_ATTRIB_WPOS][0],
162 v1->attrib[FRAG_ATTRIB_WPOS][1],
163 v1->attrib[FRAG_ATTRIB_WPOS][2]);
164 printf(" %g, %g, %g\n",
165 v2->attrib[FRAG_ATTRIB_WPOS][0],
166 v2->attrib[FRAG_ATTRIB_WPOS][1],
167 v2->attrib[FRAG_ATTRIB_WPOS][2]);
170 /* Compute fixed point x,y coords w/ half-pixel offsets and snapping.
171 * And find the order of the 3 vertices along the Y axis.
174 const GLfixed fy0
= FloatToFixed(v0
->attrib
[FRAG_ATTRIB_WPOS
][1] - 0.5F
) & snapMask
;
175 const GLfixed fy1
= FloatToFixed(v1
->attrib
[FRAG_ATTRIB_WPOS
][1] - 0.5F
) & snapMask
;
176 const GLfixed fy2
= FloatToFixed(v2
->attrib
[FRAG_ATTRIB_WPOS
][1] - 0.5F
) & snapMask
;
180 vMin
= v0
; vMid
= v1
; vMax
= v2
;
181 vMin_fy
= fy0
; vMid_fy
= fy1
; vMax_fy
= fy2
;
183 else if (fy2
<= fy0
) {
185 vMin
= v2
; vMid
= v0
; vMax
= v1
;
186 vMin_fy
= fy2
; vMid_fy
= fy0
; vMax_fy
= fy1
;
190 vMin
= v0
; vMid
= v2
; vMax
= v1
;
191 vMin_fy
= fy0
; vMid_fy
= fy2
; vMax_fy
= fy1
;
198 vMin
= v1
; vMid
= v0
; vMax
= v2
;
199 vMin_fy
= fy1
; vMid_fy
= fy0
; vMax_fy
= fy2
;
202 else if (fy2
<= fy1
) {
204 vMin
= v2
; vMid
= v1
; vMax
= v0
;
205 vMin_fy
= fy2
; vMid_fy
= fy1
; vMax_fy
= fy0
;
210 vMin
= v1
; vMid
= v2
; vMax
= v0
;
211 vMin_fy
= fy1
; vMid_fy
= fy2
; vMax_fy
= fy0
;
215 /* fixed point X coords */
216 vMin_fx
= FloatToFixed(vMin
->attrib
[FRAG_ATTRIB_WPOS
][0] + 0.5F
) & snapMask
;
217 vMid_fx
= FloatToFixed(vMid
->attrib
[FRAG_ATTRIB_WPOS
][0] + 0.5F
) & snapMask
;
218 vMax_fx
= FloatToFixed(vMax
->attrib
[FRAG_ATTRIB_WPOS
][0] + 0.5F
) & snapMask
;
221 /* vertex/edge relationship */
222 eMaj
.v0
= vMin
; eMaj
.v1
= vMax
; /*TODO: .v1's not needed */
223 eTop
.v0
= vMid
; eTop
.v1
= vMax
;
224 eBot
.v0
= vMin
; eBot
.v1
= vMid
;
226 /* compute deltas for each edge: vertex[upper] - vertex[lower] */
227 eMaj
.dx
= FixedToFloat(vMax_fx
- vMin_fx
);
228 eMaj
.dy
= FixedToFloat(vMax_fy
- vMin_fy
);
229 eTop
.dx
= FixedToFloat(vMax_fx
- vMid_fx
);
230 eTop
.dy
= FixedToFloat(vMax_fy
- vMid_fy
);
231 eBot
.dx
= FixedToFloat(vMid_fx
- vMin_fx
);
232 eBot
.dy
= FixedToFloat(vMid_fy
- vMin_fy
);
234 /* compute area, oneOverArea and perform backface culling */
236 const GLfloat area
= eMaj
.dx
* eBot
.dy
- eBot
.dx
* eMaj
.dy
;
238 if (IS_INF_OR_NAN(area
) || area
== 0.0F
)
241 if (area
* bf
* swrast
->_BackfaceCullSign
< 0.0)
244 oneOverArea
= 1.0F
/ area
;
246 /* 0 = front, 1 = back */
247 span
.facing
= oneOverArea
* bf
> 0.0F
;
250 /* Edge setup. For a triangle strip these could be reused... */
252 eMaj
.fsy
= FixedCeil(vMin_fy
);
253 eMaj
.lines
= FixedToInt(FixedCeil(vMax_fy
- eMaj
.fsy
));
254 if (eMaj
.lines
> 0) {
255 eMaj
.dxdy
= eMaj
.dx
/ eMaj
.dy
;
256 eMaj
.fdxdy
= SignedFloatToFixed(eMaj
.dxdy
);
257 eMaj
.adjy
= (GLfloat
) (eMaj
.fsy
- vMin_fy
); /* SCALED! */
259 eMaj
.fsx
= eMaj
.fx0
+ (GLfixed
) (eMaj
.adjy
* eMaj
.dxdy
);
265 eTop
.fsy
= FixedCeil(vMid_fy
);
266 eTop
.lines
= FixedToInt(FixedCeil(vMax_fy
- eTop
.fsy
));
267 if (eTop
.lines
> 0) {
268 eTop
.dxdy
= eTop
.dx
/ eTop
.dy
;
269 eTop
.fdxdy
= SignedFloatToFixed(eTop
.dxdy
);
270 eTop
.adjy
= (GLfloat
) (eTop
.fsy
- vMid_fy
); /* SCALED! */
272 eTop
.fsx
= eTop
.fx0
+ (GLfixed
) (eTop
.adjy
* eTop
.dxdy
);
275 eBot
.fsy
= FixedCeil(vMin_fy
);
276 eBot
.lines
= FixedToInt(FixedCeil(vMid_fy
- eBot
.fsy
));
277 if (eBot
.lines
> 0) {
278 eBot
.dxdy
= eBot
.dx
/ eBot
.dy
;
279 eBot
.fdxdy
= SignedFloatToFixed(eBot
.dxdy
);
280 eBot
.adjy
= (GLfloat
) (eBot
.fsy
- vMin_fy
); /* SCALED! */
282 eBot
.fsx
= eBot
.fx0
+ (GLfixed
) (eBot
.adjy
* eBot
.dxdy
);
287 * Conceptually, we view a triangle as two subtriangles
288 * separated by a perfectly horizontal line. The edge that is
289 * intersected by this line is one with maximal absolute dy; we
290 * call it a ``major'' edge. The other two edges are the
291 * ``top'' edge (for the upper subtriangle) and the ``bottom''
292 * edge (for the lower subtriangle). If either of these two
293 * edges is horizontal or very close to horizontal, the
294 * corresponding subtriangle might cover zero sample points;
295 * we take care to handle such cases, for performance as well
298 * By stepping rasterization parameters along the major edge,
299 * we can avoid recomputing them at the discontinuity where
300 * the top and bottom edges meet. However, this forces us to
301 * be able to scan both left-to-right and right-to-left.
302 * Also, we must determine whether the major edge is at the
303 * left or right side of the triangle. We do this by
304 * computing the magnitude of the cross-product of the major
305 * and top edges. Since this magnitude depends on the sine of
306 * the angle between the two edges, its sign tells us whether
307 * we turn to the left or to the right when travelling along
308 * the major edge to the top edge, and from this we infer
309 * whether the major edge is on the left or the right.
311 * Serendipitously, this cross-product magnitude is also a
312 * value we need to compute the iteration parameter
313 * derivatives for the triangle, and it can be used to perform
314 * backface culling because its sign tells us whether the
315 * triangle is clockwise or counterclockwise. In this code we
316 * refer to it as ``area'' because it's also proportional to
317 * the pixel area of the triangle.
321 GLint scan_from_left_to_right
; /* true if scanning left-to-right */
327 * Execute user-supplied setup code
333 scan_from_left_to_right
= (oneOverArea
< 0.0F
);
336 /* compute d?/dx and d?/dy derivatives */
338 span
.interpMask
|= SPAN_Z
;
340 GLfloat eMaj_dz
= vMax
->attrib
[FRAG_ATTRIB_WPOS
][2] - vMin
->attrib
[FRAG_ATTRIB_WPOS
][2];
341 GLfloat eBot_dz
= vMid
->attrib
[FRAG_ATTRIB_WPOS
][2] - vMin
->attrib
[FRAG_ATTRIB_WPOS
][2];
342 span
.attrStepX
[FRAG_ATTRIB_WPOS
][2] = oneOverArea
* (eMaj_dz
* eBot
.dy
- eMaj
.dy
* eBot_dz
);
343 if (span
.attrStepX
[FRAG_ATTRIB_WPOS
][2] > maxDepth
||
344 span
.attrStepX
[FRAG_ATTRIB_WPOS
][2] < -maxDepth
) {
345 /* probably a sliver triangle */
346 span
.attrStepX
[FRAG_ATTRIB_WPOS
][2] = 0.0;
347 span
.attrStepY
[FRAG_ATTRIB_WPOS
][2] = 0.0;
350 span
.attrStepY
[FRAG_ATTRIB_WPOS
][2] = oneOverArea
* (eMaj
.dx
* eBot_dz
- eMaj_dz
* eBot
.dx
);
353 span
.zStep
= SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_WPOS
][2]);
355 span
.zStep
= (GLint
) span
.attrStepX
[FRAG_ATTRIB_WPOS
][2];
359 span
.interpMask
|= SPAN_RGBA
;
360 if (ctx
->Light
.ShadeModel
== GL_SMOOTH
) {
361 GLfloat eMaj_dr
= (GLfloat
) (vMax
->color
[RCOMP
] - vMin
->color
[RCOMP
]);
362 GLfloat eBot_dr
= (GLfloat
) (vMid
->color
[RCOMP
] - vMin
->color
[RCOMP
]);
363 GLfloat eMaj_dg
= (GLfloat
) (vMax
->color
[GCOMP
] - vMin
->color
[GCOMP
]);
364 GLfloat eBot_dg
= (GLfloat
) (vMid
->color
[GCOMP
] - vMin
->color
[GCOMP
]);
365 GLfloat eMaj_db
= (GLfloat
) (vMax
->color
[BCOMP
] - vMin
->color
[BCOMP
]);
366 GLfloat eBot_db
= (GLfloat
) (vMid
->color
[BCOMP
] - vMin
->color
[BCOMP
]);
368 GLfloat eMaj_da
= (GLfloat
) (vMax
->color
[ACOMP
] - vMin
->color
[ACOMP
]);
369 GLfloat eBot_da
= (GLfloat
) (vMid
->color
[ACOMP
] - vMin
->color
[ACOMP
]);
371 span
.attrStepX
[FRAG_ATTRIB_COL0
][0] = oneOverArea
* (eMaj_dr
* eBot
.dy
- eMaj
.dy
* eBot_dr
);
372 span
.attrStepY
[FRAG_ATTRIB_COL0
][0] = oneOverArea
* (eMaj
.dx
* eBot_dr
- eMaj_dr
* eBot
.dx
);
373 span
.attrStepX
[FRAG_ATTRIB_COL0
][1] = oneOverArea
* (eMaj_dg
* eBot
.dy
- eMaj
.dy
* eBot_dg
);
374 span
.attrStepY
[FRAG_ATTRIB_COL0
][1] = oneOverArea
* (eMaj
.dx
* eBot_dg
- eMaj_dg
* eBot
.dx
);
375 span
.attrStepX
[FRAG_ATTRIB_COL0
][2] = oneOverArea
* (eMaj_db
* eBot
.dy
- eMaj
.dy
* eBot_db
);
376 span
.attrStepY
[FRAG_ATTRIB_COL0
][2] = oneOverArea
* (eMaj
.dx
* eBot_db
- eMaj_db
* eBot
.dx
);
377 span
.redStep
= SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_COL0
][0]);
378 span
.greenStep
= SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_COL0
][1]);
379 span
.blueStep
= SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_COL0
][2]);
381 span
.attrStepX
[FRAG_ATTRIB_COL0
][3] = oneOverArea
* (eMaj_da
* eBot
.dy
- eMaj
.dy
* eBot_da
);
382 span
.attrStepY
[FRAG_ATTRIB_COL0
][3] = oneOverArea
* (eMaj
.dx
* eBot_da
- eMaj_da
* eBot
.dx
);
383 span
.alphaStep
= SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_COL0
][3]);
384 # endif /* INTERP_ALPHA */
387 ASSERT(ctx
->Light
.ShadeModel
== GL_FLAT
);
388 span
.interpMask
|= SPAN_FLAT
;
389 span
.attrStepX
[FRAG_ATTRIB_COL0
][0] = span
.attrStepY
[FRAG_ATTRIB_COL0
][0] = 0.0F
;
390 span
.attrStepX
[FRAG_ATTRIB_COL0
][1] = span
.attrStepY
[FRAG_ATTRIB_COL0
][1] = 0.0F
;
391 span
.attrStepX
[FRAG_ATTRIB_COL0
][2] = span
.attrStepY
[FRAG_ATTRIB_COL0
][2] = 0.0F
;
396 span
.attrStepX
[FRAG_ATTRIB_COL0
][3] = span
.attrStepY
[FRAG_ATTRIB_COL0
][3] = 0.0F
;
400 #endif /* INTERP_RGB */
402 span
.interpMask
|= SPAN_INDEX
;
403 if (ctx
->Light
.ShadeModel
== GL_SMOOTH
) {
404 GLfloat eMaj_di
= vMax
->attrib
[FRAG_ATTRIB_CI
][0] - vMin
->attrib
[FRAG_ATTRIB_CI
][0];
405 GLfloat eBot_di
= vMid
->attrib
[FRAG_ATTRIB_CI
][0] - vMin
->attrib
[FRAG_ATTRIB_CI
][0];
406 didx
= oneOverArea
* (eMaj_di
* eBot
.dy
- eMaj
.dy
* eBot_di
);
407 didy
= oneOverArea
* (eMaj
.dx
* eBot_di
- eMaj_di
* eBot
.dx
);
408 span
.indexStep
= SignedFloatToFixed(didx
);
411 span
.interpMask
|= SPAN_FLAT
;
416 #ifdef INTERP_INT_TEX
418 GLfloat eMaj_ds
= (vMax
->attrib
[FRAG_ATTRIB_TEX0
][0] - vMin
->attrib
[FRAG_ATTRIB_TEX0
][0]) * S_SCALE
;
419 GLfloat eBot_ds
= (vMid
->attrib
[FRAG_ATTRIB_TEX0
][0] - vMin
->attrib
[FRAG_ATTRIB_TEX0
][0]) * S_SCALE
;
420 GLfloat eMaj_dt
= (vMax
->attrib
[FRAG_ATTRIB_TEX0
][1] - vMin
->attrib
[FRAG_ATTRIB_TEX0
][1]) * T_SCALE
;
421 GLfloat eBot_dt
= (vMid
->attrib
[FRAG_ATTRIB_TEX0
][1] - vMin
->attrib
[FRAG_ATTRIB_TEX0
][1]) * T_SCALE
;
422 span
.attrStepX
[FRAG_ATTRIB_TEX0
][0] = oneOverArea
* (eMaj_ds
* eBot
.dy
- eMaj
.dy
* eBot_ds
);
423 span
.attrStepY
[FRAG_ATTRIB_TEX0
][0] = oneOverArea
* (eMaj
.dx
* eBot_ds
- eMaj_ds
* eBot
.dx
);
424 span
.attrStepX
[FRAG_ATTRIB_TEX0
][1] = oneOverArea
* (eMaj_dt
* eBot
.dy
- eMaj
.dy
* eBot_dt
);
425 span
.attrStepY
[FRAG_ATTRIB_TEX0
][1] = oneOverArea
* (eMaj
.dx
* eBot_dt
- eMaj_dt
* eBot
.dx
);
426 span
.intTexStep
[0] = SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_TEX0
][0]);
427 span
.intTexStep
[1] = SignedFloatToFixed(span
.attrStepX
[FRAG_ATTRIB_TEX0
][1]);
430 #ifdef INTERP_ATTRIBS
432 /* attrib[FRAG_ATTRIB_WPOS][3] is 1/W */
433 const GLfloat wMax
= vMax
->attrib
[FRAG_ATTRIB_WPOS
][3];
434 const GLfloat wMin
= vMin
->attrib
[FRAG_ATTRIB_WPOS
][3];
435 const GLfloat wMid
= vMid
->attrib
[FRAG_ATTRIB_WPOS
][3];
437 const GLfloat eMaj_dw
= wMax
- wMin
;
438 const GLfloat eBot_dw
= wMid
- wMin
;
439 span
.attrStepX
[FRAG_ATTRIB_WPOS
][3] = oneOverArea
* (eMaj_dw
* eBot
.dy
- eMaj
.dy
* eBot_dw
);
440 span
.attrStepY
[FRAG_ATTRIB_WPOS
][3] = oneOverArea
* (eMaj
.dx
* eBot_dw
- eMaj_dw
* eBot
.dx
);
443 if (swrast
->_InterpMode
[attr
] == GL_FLAT
) {
444 ASSIGN_4V(span
.attrStepX
[attr
], 0.0, 0.0, 0.0, 0.0);
445 ASSIGN_4V(span
.attrStepY
[attr
], 0.0, 0.0, 0.0, 0.0);
449 for (c
= 0; c
< 4; c
++) {
450 GLfloat eMaj_da
= vMax
->attrib
[attr
][c
] * wMax
- vMin
->attrib
[attr
][c
] * wMin
;
451 GLfloat eBot_da
= vMid
->attrib
[attr
][c
] * wMid
- vMin
->attrib
[attr
][c
] * wMin
;
452 span
.attrStepX
[attr
][c
] = oneOverArea
* (eMaj_da
* eBot
.dy
- eMaj
.dy
* eBot_da
);
453 span
.attrStepY
[attr
][c
] = oneOverArea
* (eMaj
.dx
* eBot_da
- eMaj_da
* eBot
.dx
);
461 * We always sample at pixel centers. However, we avoid
462 * explicit half-pixel offsets in this code by incorporating
463 * the proper offset in each of x and y during the
464 * transformation to window coordinates.
466 * We also apply the usual rasterization rules to prevent
467 * cracks and overlaps. A pixel is considered inside a
468 * subtriangle if it meets all of four conditions: it is on or
469 * to the right of the left edge, strictly to the left of the
470 * right edge, on or below the top edge, and strictly above
471 * the bottom edge. (Some edges may be degenerate.)
473 * The following discussion assumes left-to-right scanning
474 * (that is, the major edge is on the left); the right-to-left
475 * case is a straightforward variation.
477 * We start by finding the half-integral y coordinate that is
478 * at or below the top of the triangle. This gives us the
479 * first scan line that could possibly contain pixels that are
480 * inside the triangle.
482 * Next we creep down the major edge until we reach that y,
483 * and compute the corresponding x coordinate on the edge.
484 * Then we find the half-integral x that lies on or just
485 * inside the edge. This is the first pixel that might lie in
486 * the interior of the triangle. (We won't know for sure
487 * until we check the other edges.)
489 * As we rasterize the triangle, we'll step down the major
490 * edge. For each step in y, we'll move an integer number
491 * of steps in x. There are two possible x step sizes, which
492 * we'll call the ``inner'' step (guaranteed to land on the
493 * edge or inside it) and the ``outer'' step (guaranteed to
494 * land on the edge or outside it). The inner and outer steps
495 * differ by one. During rasterization we maintain an error
496 * term that indicates our distance from the true edge, and
497 * select either the inner step or the outer step, whichever
498 * gets us to the first pixel that falls inside the triangle.
500 * All parameters (z, red, etc.) as well as the buffer
501 * addresses for color and z have inner and outer step values,
502 * so that we can increment them appropriately. This method
503 * eliminates the need to adjust parameters by creeping a
504 * sub-pixel amount into the triangle at each scanline.
509 GLfixed fxLeftEdge
= 0, fxRightEdge
= 0;
510 GLfixed fdxLeftEdge
= 0, fdxRightEdge
= 0;
511 GLfixed fError
= 0, fdError
= 0;
513 PIXEL_TYPE
*pRow
= NULL
;
514 GLint dPRowOuter
= 0, dPRowInner
; /* offset in bytes */
518 struct gl_renderbuffer
*zrb
519 = ctx
->DrawBuffer
->Attachment
[BUFFER_DEPTH
].Renderbuffer
;
520 DEPTH_TYPE
*zRow
= NULL
;
521 GLint dZRowOuter
= 0, dZRowInner
; /* offset in bytes */
524 GLfixed fdzOuter
= 0, fdzInner
;
527 GLint rLeft
= 0, fdrOuter
= 0, fdrInner
;
528 GLint gLeft
= 0, fdgOuter
= 0, fdgInner
;
529 GLint bLeft
= 0, fdbOuter
= 0, fdbInner
;
532 GLint aLeft
= 0, fdaOuter
= 0, fdaInner
;
535 GLfixed iLeft
=0, diOuter
=0, diInner
;
537 #ifdef INTERP_INT_TEX
538 GLfixed sLeft
=0, dsOuter
=0, dsInner
;
539 GLfixed tLeft
=0, dtOuter
=0, dtInner
;
541 #ifdef INTERP_ATTRIBS
542 GLfloat wLeft
= 0, dwOuter
= 0, dwInner
;
543 GLfloat attrLeft
[FRAG_ATTRIB_MAX
][4];
544 GLfloat daOuter
[FRAG_ATTRIB_MAX
][4], daInner
[FRAG_ATTRIB_MAX
][4];
547 for (subTriangle
=0; subTriangle
<=1; subTriangle
++) {
548 EdgeT
*eLeft
, *eRight
;
549 int setupLeft
, setupRight
;
552 if (subTriangle
==0) {
554 if (scan_from_left_to_right
) {
557 lines
= eRight
->lines
;
564 lines
= eLeft
->lines
;
571 if (scan_from_left_to_right
) {
574 lines
= eRight
->lines
;
581 lines
= eLeft
->lines
;
589 if (setupLeft
&& eLeft
->lines
> 0) {
590 const SWvertex
*vLower
= eLeft
->v0
;
591 const GLfixed fsy
= eLeft
->fsy
;
592 const GLfixed fsx
= eLeft
->fsx
; /* no fractional part */
593 const GLfixed fx
= FixedCeil(fsx
); /* no fractional part */
594 const GLfixed adjx
= (GLfixed
) (fx
- eLeft
->fx0
); /* SCALED! */
595 const GLfixed adjy
= (GLfixed
) eLeft
->adjy
; /* SCALED! */
600 fError
= fx
- fsx
- FIXED_ONE
;
601 fxLeftEdge
= fsx
- FIXED_EPSILON
;
602 fdxLeftEdge
= eLeft
->fdxdy
;
603 fdxOuter
= FixedFloor(fdxLeftEdge
- FIXED_EPSILON
);
604 fdError
= fdxOuter
- fdxLeftEdge
+ FIXED_ONE
;
605 idxOuter
= FixedToInt(fdxOuter
);
606 dxOuter
= (GLfloat
) idxOuter
;
607 span
.y
= FixedToInt(fsy
);
609 /* silence warnings on some compilers */
617 pRow
= (PIXEL_TYPE
*) PIXEL_ADDRESS(FixedToInt(fxLeftEdge
), span
.y
);
618 dPRowOuter
= -((int)BYTES_PER_ROW
) + idxOuter
* sizeof(PIXEL_TYPE
);
619 /* negative because Y=0 at bottom and increases upward */
623 * Now we need the set of parameter (z, color, etc.) values at
624 * the point (fx, fsy). This gives us properly-sampled parameter
625 * values that we can step from pixel to pixel. Furthermore,
626 * although we might have intermediate results that overflow
627 * the normal parameter range when we step temporarily outside
628 * the triangle, we shouldn't overflow or underflow for any
629 * pixel that's actually inside the triangle.
634 GLfloat z0
= vLower
->attrib
[FRAG_ATTRIB_WPOS
][2];
635 if (depthBits
<= 16) {
636 /* interpolate fixed-pt values */
637 GLfloat tmp
= (z0
* FIXED_SCALE
638 + span
.attrStepX
[FRAG_ATTRIB_WPOS
][2] * adjx
639 + span
.attrStepY
[FRAG_ATTRIB_WPOS
][2] * adjy
) + FIXED_HALF
;
640 if (tmp
< MAX_GLUINT
/ 2)
641 zLeft
= (GLfixed
) tmp
;
643 zLeft
= MAX_GLUINT
/ 2;
644 fdzOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_WPOS
][2] +
645 dxOuter
* span
.attrStepX
[FRAG_ATTRIB_WPOS
][2]);
648 /* interpolate depth values w/out scaling */
649 zLeft
= (GLuint
) (z0
+ span
.attrStepX
[FRAG_ATTRIB_WPOS
][2] * FixedToFloat(adjx
)
650 + span
.attrStepY
[FRAG_ATTRIB_WPOS
][2] * FixedToFloat(adjy
));
651 fdzOuter
= (GLint
) (span
.attrStepY
[FRAG_ATTRIB_WPOS
][2] +
652 dxOuter
* span
.attrStepX
[FRAG_ATTRIB_WPOS
][2]);
655 zRow
= (DEPTH_TYPE
*)
656 zrb
->GetPointer(ctx
, zrb
, FixedToInt(fxLeftEdge
), span
.y
);
657 dZRowOuter
= (ctx
->DrawBuffer
->Width
+ idxOuter
) * sizeof(DEPTH_TYPE
);
662 if (ctx
->Light
.ShadeModel
== GL_SMOOTH
) {
663 rLeft
= (GLint
)(ChanToFixed(vLower
->color
[RCOMP
])
664 + span
.attrStepX
[FRAG_ATTRIB_COL0
][0] * adjx
665 + span
.attrStepY
[FRAG_ATTRIB_COL0
][0] * adjy
) + FIXED_HALF
;
666 gLeft
= (GLint
)(ChanToFixed(vLower
->color
[GCOMP
])
667 + span
.attrStepX
[FRAG_ATTRIB_COL0
][1] * adjx
668 + span
.attrStepY
[FRAG_ATTRIB_COL0
][1] * adjy
) + FIXED_HALF
;
669 bLeft
= (GLint
)(ChanToFixed(vLower
->color
[BCOMP
])
670 + span
.attrStepX
[FRAG_ATTRIB_COL0
][2] * adjx
671 + span
.attrStepY
[FRAG_ATTRIB_COL0
][2] * adjy
) + FIXED_HALF
;
672 fdrOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_COL0
][0]
673 + dxOuter
* span
.attrStepX
[FRAG_ATTRIB_COL0
][0]);
674 fdgOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_COL0
][1]
675 + dxOuter
* span
.attrStepX
[FRAG_ATTRIB_COL0
][1]);
676 fdbOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_COL0
][2]
677 + dxOuter
* span
.attrStepX
[FRAG_ATTRIB_COL0
][2]);
679 aLeft
= (GLint
)(ChanToFixed(vLower
->color
[ACOMP
])
680 + span
.attrStepX
[FRAG_ATTRIB_COL0
][3] * adjx
681 + span
.attrStepY
[FRAG_ATTRIB_COL0
][3] * adjy
) + FIXED_HALF
;
682 fdaOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_COL0
][3]
683 + dxOuter
* span
.attrStepX
[FRAG_ATTRIB_COL0
][3]);
687 ASSERT(ctx
->Light
.ShadeModel
== GL_FLAT
);
688 rLeft
= ChanToFixed(v2
->color
[RCOMP
]);
689 gLeft
= ChanToFixed(v2
->color
[GCOMP
]);
690 bLeft
= ChanToFixed(v2
->color
[BCOMP
]);
691 fdrOuter
= fdgOuter
= fdbOuter
= 0;
693 aLeft
= ChanToFixed(v2
->color
[ACOMP
]);
697 #endif /* INTERP_RGB */
701 if (ctx
->Light
.ShadeModel
== GL_SMOOTH
) {
702 iLeft
= (GLfixed
)(vLower
->attrib
[FRAG_ATTRIB_CI
][0] * FIXED_SCALE
703 + didx
* adjx
+ didy
* adjy
) + FIXED_HALF
;
704 diOuter
= SignedFloatToFixed(didy
+ dxOuter
* didx
);
707 ASSERT(ctx
->Light
.ShadeModel
== GL_FLAT
);
708 iLeft
= FloatToFixed(v2
->attrib
[FRAG_ATTRIB_CI
][0]);
712 #ifdef INTERP_INT_TEX
715 s0
= vLower
->attrib
[FRAG_ATTRIB_TEX0
][0] * S_SCALE
;
716 sLeft
= (GLfixed
)(s0
* FIXED_SCALE
+ span
.attrStepX
[FRAG_ATTRIB_TEX0
][0] * adjx
717 + span
.attrStepY
[FRAG_ATTRIB_TEX0
][0] * adjy
) + FIXED_HALF
;
718 dsOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_TEX0
][0]
719 + dxOuter
* span
.attrStepX
[FRAG_ATTRIB_TEX0
][0]);
721 t0
= vLower
->attrib
[FRAG_ATTRIB_TEX0
][1] * T_SCALE
;
722 tLeft
= (GLfixed
)(t0
* FIXED_SCALE
+ span
.attrStepX
[FRAG_ATTRIB_TEX0
][1] * adjx
723 + span
.attrStepY
[FRAG_ATTRIB_TEX0
][1] * adjy
) + FIXED_HALF
;
724 dtOuter
= SignedFloatToFixed(span
.attrStepY
[FRAG_ATTRIB_TEX0
][1]
725 + dxOuter
* span
.attrStepX
[FRAG_ATTRIB_TEX0
][1]);
728 #ifdef INTERP_ATTRIBS
730 const GLuint attr
= FRAG_ATTRIB_WPOS
;
731 wLeft
= vLower
->attrib
[FRAG_ATTRIB_WPOS
][3]
732 + (span
.attrStepX
[attr
][3] * adjx
733 + span
.attrStepY
[attr
][3] * adjy
) * (1.0F
/FIXED_SCALE
);
734 dwOuter
= span
.attrStepY
[attr
][3] + dxOuter
* span
.attrStepX
[attr
][3];
737 const GLfloat invW
= vLower
->attrib
[FRAG_ATTRIB_WPOS
][3];
738 if (swrast
->_InterpMode
[attr
] == GL_FLAT
) {
740 for (c
= 0; c
< 4; c
++) {
741 attrLeft
[attr
][c
] = v2
->attrib
[attr
][c
] * invW
;
742 daOuter
[attr
][c
] = 0.0;
747 for (c
= 0; c
< 4; c
++) {
748 const GLfloat a
= vLower
->attrib
[attr
][c
] * invW
;
749 attrLeft
[attr
][c
] = a
+ ( span
.attrStepX
[attr
][c
] * adjx
750 + span
.attrStepY
[attr
][c
] * adjy
) * (1.0F
/FIXED_SCALE
);
751 daOuter
[attr
][c
] = span
.attrStepY
[attr
][c
] + dxOuter
* span
.attrStepX
[attr
][c
];
759 if (setupRight
&& eRight
->lines
>0) {
760 fxRightEdge
= eRight
->fsx
- FIXED_EPSILON
;
761 fdxRightEdge
= eRight
->fdxdy
;
769 /* Rasterize setup */
771 dPRowInner
= dPRowOuter
+ sizeof(PIXEL_TYPE
);
775 dZRowInner
= dZRowOuter
+ sizeof(DEPTH_TYPE
);
777 fdzInner
= fdzOuter
+ span
.zStep
;
780 fdrInner
= fdrOuter
+ span
.redStep
;
781 fdgInner
= fdgOuter
+ span
.greenStep
;
782 fdbInner
= fdbOuter
+ span
.blueStep
;
785 fdaInner
= fdaOuter
+ span
.alphaStep
;
788 diInner
= diOuter
+ span
.indexStep
;
790 #ifdef INTERP_INT_TEX
791 dsInner
= dsOuter
+ span
.intTexStep
[0];
792 dtInner
= dtOuter
+ span
.intTexStep
[1];
794 #ifdef INTERP_ATTRIBS
795 dwInner
= dwOuter
+ span
.attrStepX
[FRAG_ATTRIB_WPOS
][3];
798 for (c
= 0; c
< 4; c
++) {
799 daInner
[attr
][c
] = daOuter
[attr
][c
] + span
.attrStepX
[attr
][c
];
805 /* initialize the span interpolants to the leftmost value */
806 /* ff = fixed-pt fragment */
807 const GLint right
= FixedToInt(fxRightEdge
);
808 span
.x
= FixedToInt(fxLeftEdge
);
812 span
.end
= right
- span
.x
;
828 #ifdef INTERP_INT_TEX
829 span
.intTex
[0] = sLeft
;
830 span
.intTex
[1] = tLeft
;
833 #ifdef INTERP_ATTRIBS
834 span
.attrStart
[FRAG_ATTRIB_WPOS
][3] = wLeft
;
837 for (c
= 0; c
< 4; c
++) {
838 span
.attrStart
[attr
][c
] = attrLeft
[attr
][c
];
843 /* This is where we actually generate fragments */
844 /* XXX the test for span.y > 0 _shouldn't_ be needed but
845 * it fixes a problem on 64-bit Opterons (bug 4842).
847 if (span
.end
> 0 && span
.y
>= 0) {
848 const GLint len
= span
.end
- 1;
851 CLAMP_INTERPOLANT(red
, redStep
, len
);
852 CLAMP_INTERPOLANT(green
, greenStep
, len
);
853 CLAMP_INTERPOLANT(blue
, blueStep
, len
);
856 CLAMP_INTERPOLANT(alpha
, alphaStep
, len
);
859 CLAMP_INTERPOLANT(index
, indexStep
, len
);
867 * Advance to the next scan line. Compute the
868 * new edge coordinates, and adjust the
869 * pixel-center x coordinate so that it stays
870 * on or inside the major edge.
875 fxLeftEdge
+= fdxLeftEdge
;
876 fxRightEdge
+= fdxRightEdge
;
883 pRow
= (PIXEL_TYPE
*) ((GLubyte
*) pRow
+ dPRowOuter
);
887 zRow
= (DEPTH_TYPE
*) ((GLubyte
*) zRow
+ dZRowOuter
);
902 #ifdef INTERP_INT_TEX
906 #ifdef INTERP_ATTRIBS
910 for (c
= 0; c
< 4; c
++) {
911 attrLeft
[attr
][c
] += daOuter
[attr
][c
];
918 pRow
= (PIXEL_TYPE
*) ((GLubyte
*) pRow
+ dPRowInner
);
922 zRow
= (DEPTH_TYPE
*) ((GLubyte
*) zRow
+ dZRowInner
);
937 #ifdef INTERP_INT_TEX
941 #ifdef INTERP_ATTRIBS
945 for (c
= 0; c
< 4; c
++) {
946 attrLeft
[attr
][c
] += daInner
[attr
][c
];
953 } /* for subTriangle */
971 #undef INTERP_INT_TEX
972 #undef INTERP_ATTRIBS