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1 /**************************************************************************
2  *
3  * Copyright 2007 VMware, Inc.
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 VMWARE 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 <keithw@vmware.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 
38 struct 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 
twoside_stage(struct draw_stage * stage)46 static 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  */
54 static inline struct vertex_header *
copy_bfc(struct twoside_stage * twoside,const struct vertex_header * v,unsigned idx)55 copy_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  */
twoside_tri(struct draw_stage * stage,struct prim_header * header)76 static 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 
twoside_first_tri(struct draw_stage * stage,struct prim_header * header)102 static 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 
twoside_flush(struct draw_stage * stage,unsigned flags)142 static 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 
twoside_reset_stipple_counter(struct draw_stage * stage)149 static void twoside_reset_stipple_counter( struct draw_stage *stage )
150 {
151    stage->next->reset_stipple_counter( stage->next );
152 }
153 
154 
twoside_destroy(struct draw_stage * stage)155 static 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  */
draw_twoside_stage(struct draw_context * draw)165 struct draw_stage *draw_twoside_stage( struct draw_context *draw )
166 {
167    struct twoside_stage *twoside = CALLOC_STRUCT(twoside_stage);
168    if (!twoside)
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