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 "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    uint attrib_front0, attrib_back0;
  42    uint attrib_front1, attrib_back1;
  43 };
  44
  45
  46 static INLINE struct twoside_stage *twoside_stage( struct draw_stage *stage )
  47 {
  48    return (struct twoside_stage *)stage;
  49 }
  50
  51
  52
  53
  54 /**
  55  * Copy back color(s) to front color(s).
  56  */
  57 static INLINE struct vertex_header *
  58 copy_bfc( struct twoside_stage *twoside,
  59           const struct vertex_header *v,
  60           unsigned idx )
  61 {
  62    struct vertex_header *tmp = dup_vert( &twoside->stage, v, idx );
  63
  64    if (twoside->attrib_back0) {
  65       COPY_4FV(tmp->data[twoside->attrib_front0],
  66                tmp->data[twoside->attrib_back0]);
  67    }
  68    if (twoside->attrib_back1) {
  69       COPY_4FV(tmp->data[twoside->attrib_front1],
  70                tmp->data[twoside->attrib_back1]);
  71    }
  72
  73    return tmp;
  74 }
  75
  76
  77 /* Twoside tri:
  78  */
  79 static void twoside_tri( struct draw_stage *stage,
  80                          struct prim_header *header )
  81 {
  82    struct twoside_stage *twoside = twoside_stage(stage);
  83
  84    if (header->det * twoside->sign < 0.0) {
  85       /* this is a back-facing triangle */
  86       struct prim_header tmp;
  87
  88       tmp.det = header->det;
  89       tmp.flags = header->flags;
  90       tmp.pad = header->pad;
  91       /* copy back attribs to front attribs */
  92       tmp.v[0] = copy_bfc(twoside, header->v[0], 0);
  93       tmp.v[1] = copy_bfc(twoside, header->v[1], 1);
  94       tmp.v[2] = copy_bfc(twoside, header->v[2], 2);
  95
  96       stage->next->tri( stage->next, &tmp );
  97    }
  98    else {
  99       stage->next->tri( stage->next, header );
 100    }
 101 }
 102
 103
 104
 105 static void twoside_first_tri( struct draw_stage *stage,
 106                                struct prim_header *header )
 107 {
 108    struct twoside_stage *twoside = twoside_stage(stage);
 109    const struct draw_vertex_shader *vs = stage->draw->vs.vertex_shader;
 110    uint i;
 111
 112    twoside->attrib_front0 = 0;
 113    twoside->attrib_front1 = 0;
 114    twoside->attrib_back0 = 0;
 115    twoside->attrib_back1 = 0;
 116
 117    /* Find which vertex shader outputs are front/back colors */
 118    for (i = 0; i < vs->info.num_outputs; i++) {
 119       if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR) {
 120          if (vs->info.output_semantic_index[i] == 0)
 121             twoside->attrib_front0 = i;
 122          else
 123             twoside->attrib_front1 = i;
 124       }
 125       if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
 126          if (vs->info.output_semantic_index[i] == 0)
 127             twoside->attrib_back0 = i;
 128          else
 129             twoside->attrib_back1 = i;
 130       }
 131    }
 132
 133    if (!twoside->attrib_back0)
 134       twoside->attrib_front0 = 0;
 135
 136    if (!twoside->attrib_back1)
 137       twoside->attrib_front1 = 0;
 138
 139    /*
 140     * We'll multiply the primitive's determinant by this sign to determine
 141     * if the triangle is back-facing (negative).
 142     * sign = -1 for CCW, +1 for CW
 143     */
 144    twoside->sign = stage->draw->rasterizer->front_ccw ? -1.0f : 1.0f;
 145
 146    stage->tri = twoside_tri;
 147    stage->tri( stage, header );
 148 }
 149
 150
 151 static void twoside_flush( struct draw_stage *stage, unsigned flags )
 152 {
 153    stage->tri = twoside_first_tri;
 154    stage->next->flush( stage->next, flags );
 155 }
 156
 157
 158 static void twoside_reset_stipple_counter( struct draw_stage *stage )
 159 {
 160    stage->next->reset_stipple_counter( stage->next );
 161 }
 162
 163
 164 static void twoside_destroy( struct draw_stage *stage )
 165 {
 166    draw_free_temp_verts( stage );
 167    FREE( stage );
 168 }
 169
 170
 171 /**
 172  * Create twoside pipeline stage.
 173  */
 174 struct draw_stage *draw_twoside_stage( struct draw_context *draw )
 175 {
 176    struct twoside_stage *twoside = CALLOC_STRUCT(twoside_stage);
 177    if (twoside == NULL)
 178       goto fail;
 179
 180    twoside->stage.draw = draw;
 181    twoside->stage.name = "twoside";
 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    if (!draw_alloc_temp_verts( &twoside->stage, 3 ))
 191       goto fail;
 192
 193    return &twoside->stage;
 194
 195  fail:
 196    if (twoside)
 197       twoside->stage.destroy( &twoside->stage );
 198
 199    return NULL;
 200 }