1/**************************************************************************
2 *
3 * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
4 * All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sub license, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
16 * of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21 * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
22 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 *
26 **************************************************************************/
27
28/* Authors:  Keith Whitwell <keith@tungstengraphics.com>
29 */
30
31#include "util/u_math.h"
32#include "util/u_memory.h"
33#include "pipe/p_defines.h"
34#include "pipe/p_shader_tokens.h"
35#include "draw_vs.h"
36#include "draw_pipe.h"
37
38struct twoside_stage {
39   struct draw_stage stage;
40   float sign;         /**< +1 or -1 */
41   int attrib_front0, attrib_back0;
42   int attrib_front1, attrib_back1;
43};
44
45
46static INLINE struct twoside_stage *twoside_stage( struct draw_stage *stage )
47{
48   return (struct twoside_stage *)stage;
49}
50
51/**
52 * Copy back color(s) to front color(s).
53 */
54static INLINE struct vertex_header *
55copy_bfc( struct twoside_stage *twoside,
56          const struct vertex_header *v,
57          unsigned idx )
58{
59   struct vertex_header *tmp = dup_vert( &twoside->stage, v, idx );
60
61   if (twoside->attrib_back0 >= 0 && twoside->attrib_front0 >= 0) {
62      COPY_4FV(tmp->data[twoside->attrib_front0],
63               tmp->data[twoside->attrib_back0]);
64   }
65   if (twoside->attrib_back1 >= 0 && twoside->attrib_front1 >= 0) {
66      COPY_4FV(tmp->data[twoside->attrib_front1],
67               tmp->data[twoside->attrib_back1]);
68   }
69
70   return tmp;
71}
72
73
74/* Twoside tri:
75 */
76static void twoside_tri( struct draw_stage *stage,
77			 struct prim_header *header )
78{
79   struct twoside_stage *twoside = twoside_stage(stage);
80
81   if (header->det * twoside->sign < 0.0) {
82      /* this is a back-facing triangle */
83      struct prim_header tmp;
84
85      tmp.det = header->det;
86      tmp.flags = header->flags;
87      tmp.pad = header->pad;
88      /* copy back attribs to front attribs */
89      tmp.v[0] = copy_bfc(twoside, header->v[0], 0);
90      tmp.v[1] = copy_bfc(twoside, header->v[1], 1);
91      tmp.v[2] = copy_bfc(twoside, header->v[2], 2);
92
93      stage->next->tri( stage->next, &tmp );
94   }
95   else {
96      stage->next->tri( stage->next, header );
97   }
98}
99
100
101
102static void twoside_first_tri( struct draw_stage *stage,
103			       struct prim_header *header )
104{
105   struct twoside_stage *twoside = twoside_stage(stage);
106   const struct draw_vertex_shader *vs = stage->draw->vs.vertex_shader;
107   uint i;
108
109   twoside->attrib_front0 = -1;
110   twoside->attrib_front1 = -1;
111   twoside->attrib_back0 = -1;
112   twoside->attrib_back1 = -1;
113
114   /* Find which vertex shader outputs are front/back colors */
115   for (i = 0; i < vs->info.num_outputs; i++) {
116      if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR) {
117         if (vs->info.output_semantic_index[i] == 0)
118            twoside->attrib_front0 = i;
119         else
120            twoside->attrib_front1 = i;
121      }
122      if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
123         if (vs->info.output_semantic_index[i] == 0)
124            twoside->attrib_back0 = i;
125         else
126            twoside->attrib_back1 = i;
127      }
128   }
129
130   /*
131    * We'll multiply the primitive's determinant by this sign to determine
132    * if the triangle is back-facing (negative).
133    * sign = -1 for CCW, +1 for CW
134    */
135   twoside->sign = stage->draw->rasterizer->front_ccw ? -1.0f : 1.0f;
136
137   stage->tri = twoside_tri;
138   stage->tri( stage, header );
139}
140
141
142static void twoside_flush( struct draw_stage *stage, unsigned flags )
143{
144   stage->tri = twoside_first_tri;
145   stage->next->flush( stage->next, flags );
146}
147
148
149static void twoside_reset_stipple_counter( struct draw_stage *stage )
150{
151   stage->next->reset_stipple_counter( stage->next );
152}
153
154
155static void twoside_destroy( struct draw_stage *stage )
156{
157   draw_free_temp_verts( stage );
158   FREE( stage );
159}
160
161
162/**
163 * Create twoside pipeline stage.
164 */
165struct draw_stage *draw_twoside_stage( struct draw_context *draw )
166{
167   struct twoside_stage *twoside = CALLOC_STRUCT(twoside_stage);
168   if (twoside == NULL)
169      goto fail;
170
171   twoside->stage.draw = draw;
172   twoside->stage.name = "twoside";
173   twoside->stage.next = NULL;
174   twoside->stage.point = draw_pipe_passthrough_point;
175   twoside->stage.line = draw_pipe_passthrough_line;
176   twoside->stage.tri = twoside_first_tri;
177   twoside->stage.flush = twoside_flush;
178   twoside->stage.reset_stipple_counter = twoside_reset_stipple_counter;
179   twoside->stage.destroy = twoside_destroy;
180
181   if (!draw_alloc_temp_verts( &twoside->stage, 3 ))
182      goto fail;
183
184   return &twoside->stage;
185
186 fail:
187   if (twoside)
188      twoside->stage.destroy( &twoside->stage );
189
190   return NULL;
191}
192