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.edgeflags = header->edgeflags;
  89       /* copy back attribs to front attribs */
  90       tmp.v[0] = copy_bfc(twoside, header->v[0], 0);
  91       tmp.v[1] = copy_bfc(twoside, header->v[1], 1);
  92       tmp.v[2] = copy_bfc(twoside, header->v[2], 2);
  93
  94       stage->next->tri( stage->next, &tmp );
  95    }
  96    else {
  97       stage->next->tri( stage->next, header );
  98    }
  99 }
 100
 101
 102
 103 static void twoside_first_tri( struct draw_stage *stage,
 104                                struct prim_header *header )
 105 {
 106    struct twoside_stage *twoside = twoside_stage(stage);
 107    const struct draw_vertex_shader *vs = stage->draw->vertex_shader;
 108    uint i;
 109
 110    twoside->attrib_front0 = 0;
 111    twoside->attrib_front1 = 0;
 112    twoside->attrib_back0 = 0;
 113    twoside->attrib_back1 = 0;
 114
 115    /* Find which vertex shader outputs are front/back colors */
 116    for (i = 0; i < vs->info.num_outputs; i++) {
 117       if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR) {
 118          if (vs->info.output_semantic_index[i] == 0)
 119             twoside->attrib_front0 = i;
 120          else
 121             twoside->attrib_front1 = i;
 122       }
 123       if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
 124          if (vs->info.output_semantic_index[i] == 0)
 125             twoside->attrib_back0 = i;
 126          else
 127             twoside->attrib_back1 = i;
 128       }
 129    }
 130
 131    if (!twoside->attrib_back0)
 132       twoside->attrib_front0 = 0;
 133
 134    if (!twoside->attrib_back1)
 135       twoside->attrib_front1 = 0;
 136
 137    /*
 138     * We'll multiply the primitive's determinant by this sign to determine
 139     * if the triangle is back-facing (negative).
 140     * sign = -1 for CCW, +1 for CW
 141     */
 142    twoside->sign = (stage->draw->rasterizer->front_winding == PIPE_WINDING_CCW) ? -1.0f : 1.0f;
 143
 144    stage->tri = twoside_tri;
 145    stage->tri( stage, header );
 146 }
 147
 148
 149 static void twoside_flush( struct draw_stage *stage, unsigned flags )
 150 {
 151    stage->tri = twoside_first_tri;
 152    stage->next->flush( stage->next, flags );
 153 }
 154
 155
 156 static void twoside_reset_stipple_counter( struct draw_stage *stage )
 157 {
 158    stage->next->reset_stipple_counter( stage->next );
 159 }
 160
 161
 162 static void twoside_destroy( struct draw_stage *stage )
 163 {
 164    draw_free_temp_verts( stage );
 165    FREE( stage );
 166 }
 167
 168
 169 /**
 170  * Create twoside pipeline stage.
 171  */
 172 struct draw_stage *draw_twoside_stage( struct draw_context *draw )
 173 {
 174    struct twoside_stage *twoside = CALLOC_STRUCT(twoside_stage);
 175    if (twoside == NULL)
 176       goto fail;
 177
 178    if (!draw_alloc_temp_verts( &twoside->stage, 3 ))
 179       goto fail;
 180
 181    twoside->stage.draw = draw;
 182    twoside->stage.next = NULL;
 183    twoside->stage.point = draw_pipe_passthrough_point;
 184    twoside->stage.line = draw_pipe_passthrough_line;
 185    twoside->stage.tri = twoside_first_tri;
 186    twoside->stage.flush = twoside_flush;
 187    twoside->stage.reset_stipple_counter = twoside_reset_stipple_counter;
 188    twoside->stage.destroy = twoside_destroy;
 189
 190    return &twoside->stage;
 191
 192  fail:
 193    if (twoside)
 194       twoside->stage.destroy( &twoside->stage );
 195
 196    return NULL;
 197 }