src/gallium/auxiliary/draw/draw_pipe_twoside.c

   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 "pipe/p_util.h"
  32 #include "pipe/p_defines.h"
  33 #include "pipe/p_shader_tokens.h"
  34 #include "draw_vs.h"
  35 #include "draw_pipe.h"
  36
  37 struct twoside_stage {
  38    struct draw_stage stage;
  39    float sign;         /**< +1 or -1 */
  40    uint attrib_front0, attrib_back0;
  41    uint attrib_front1, attrib_back1;
  42 };
  43
  44
  45 static INLINE struct twoside_stage *twoside_stage( struct draw_stage *stage )
  46 {
  47    return (struct twoside_stage *)stage;
  48 }
  49
  50
  51
  52
  53 /**
  54  * Copy back color(s) to front color(s).
  55  */
  56 static INLINE struct vertex_header *
  57 copy_bfc( struct twoside_stage *twoside,
  58           const struct vertex_header *v,
  59           unsigned idx )
  60 {
  61    struct vertex_header *tmp = dup_vert( &twoside->stage, v, idx );
  62
  63    if (twoside->attrib_back0) {
  64       COPY_4FV(tmp->data[twoside->attrib_front0],
  65                tmp->data[twoside->attrib_back0]);
  66    }
  67    if (twoside->attrib_back1) {
  68       COPY_4FV(tmp->data[twoside->attrib_front1],
  69                tmp->data[twoside->attrib_back1]);
  70    }
  71
  72    return tmp;
  73 }
  74
  75
  76 /* Twoside tri:
  77  */
  78 static void twoside_tri( struct draw_stage *stage,
  79                          struct prim_header *header )
  80 {
  81    struct twoside_stage *twoside = twoside_stage(stage);
  82
  83    if (header->det * twoside->sign < 0.0) {
  84       /* this is a back-facing triangle */
  85       struct prim_header tmp;
  86
  87       tmp.det = header->det;
  88       tmp.flags = header->flags;
  89       tmp.pad = header->pad;
  90       /* copy back attribs to front attribs */
  91       tmp.v[0] = copy_bfc(twoside, header->v[0], 0);
  92       tmp.v[1] = copy_bfc(twoside, header->v[1], 1);
  93       tmp.v[2] = copy_bfc(twoside, header->v[2], 2);
  94
  95       stage->next->tri( stage->next, &tmp );
  96    }
  97    else {
  98       stage->next->tri( stage->next, header );
  99    }
 100 }
 101
 102
 103
 104 static void twoside_first_tri( struct draw_stage *stage,
 105                                struct prim_header *header )
 106 {
 107    struct twoside_stage *twoside = twoside_stage(stage);
 108    const struct draw_vertex_shader *vs = stage->draw->vertex_shader;
 109    uint i;
 110
 111    twoside->attrib_front0 = 0;
 112    twoside->attrib_front1 = 0;
 113    twoside->attrib_back0 = 0;
 114    twoside->attrib_back1 = 0;
 115
 116    /* Find which vertex shader outputs are front/back colors */
 117    for (i = 0; i < vs->info.num_outputs; i++) {
 118       if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR) {
 119          if (vs->info.output_semantic_index[i] == 0)
 120             twoside->attrib_front0 = i;
 121          else
 122             twoside->attrib_front1 = i;
 123       }
 124       if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
 125          if (vs->info.output_semantic_index[i] == 0)
 126             twoside->attrib_back0 = i;
 127          else
 128             twoside->attrib_back1 = i;
 129       }
 130    }
 131
 132    if (!twoside->attrib_back0)
 133       twoside->attrib_front0 = 0;
 134
 135    if (!twoside->attrib_back1)
 136       twoside->attrib_front1 = 0;
 137
 138    /*
 139     * We'll multiply the primitive's determinant by this sign to determine
 140     * if the triangle is back-facing (negative).
 141     * sign = -1 for CCW, +1 for CW
 142     */
 143    twoside->sign = (stage->draw->rasterizer->front_winding == PIPE_WINDING_CCW) ? -1.0f : 1.0f;
 144
 145    stage->tri = twoside_tri;
 146    stage->tri( stage, header );
 147 }
 148
 149
 150 static void twoside_flush( struct draw_stage *stage, unsigned flags )
 151 {
 152    stage->tri = twoside_first_tri;
 153    stage->next->flush( stage->next, flags );
 154 }
 155
 156
 157 static void twoside_reset_stipple_counter( struct draw_stage *stage )
 158 {
 159    stage->next->reset_stipple_counter( stage->next );
 160 }
 161
 162
 163 static void twoside_destroy( struct draw_stage *stage )
 164 {
 165    draw_free_temp_verts( stage );
 166    FREE( stage );
 167 }
 168
 169
 170 /**
 171  * Create twoside pipeline stage.
 172  */
 173 struct draw_stage *draw_twoside_stage( struct draw_context *draw )
 174 {
 175    struct twoside_stage *twoside = CALLOC_STRUCT(twoside_stage);
 176    if (twoside == NULL)
 177       goto fail;
 178
 179    if (!draw_alloc_temp_verts( &twoside->stage, 3 ))
 180       goto fail;
 181
 182    twoside->stage.draw = draw;
 183    twoside->stage.next = NULL;
 184    twoside->stage.point = draw_pipe_passthrough_point;
 185    twoside->stage.line = draw_pipe_passthrough_line;
 186    twoside->stage.tri = twoside_first_tri;
 187    twoside->stage.flush = twoside_flush;
 188    twoside->stage.reset_stipple_counter = twoside_reset_stipple_counter;
 189    twoside->stage.destroy = twoside_destroy;
 190
 191    return &twoside->stage;
 192
 193  fail:
 194    if (twoside)
 195       twoside->stage.destroy( &twoside->stage );
 196
 197    return NULL;
 198 }