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    int attrib_front0, attrib_back0;
  42    int 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  * Copy back color(s) to front color(s).
  53  */
  54 static INLINE struct vertex_header *
  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  */
  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
 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
 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
 149 static void twoside_reset_stipple_counter( struct draw_stage *stage )
 150 {
 151    stage->next->reset_stipple_counter( stage->next );
 152 }
 153
 154
 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  */
 165 struct 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 }