src/gallium/auxiliary/draw/draw_pipe_user_cull.c

   1 /**************************************************************************
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   3  * Copyright 2007 VMware, Inc.
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  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
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  26  **************************************************************************/
  27
  28 /**
  29  * \brief  Drawing stage for user culling
  30  */
  31
  32 #include "util/u_math.h"
  33 #include "util/u_memory.h"
  34 #include "pipe/p_defines.h"
  35 #include "draw_pipe.h"
  36
  37 struct user_cull_stage {
  38    struct draw_stage stage;
  39 };
  40
  41 static inline struct user_cull_stage *user_cull_stage( struct draw_stage *stage )
  42 {
  43    return (struct user_cull_stage *)stage;
  44 }
  45
  46 static inline boolean
  47 cull_distance_is_out(float dist)
  48 {
  49    return (dist < 0.0f) || util_is_inf_or_nan(dist);
  50 }
  51
  52 /*
  53  * If the shader writes the culldistance then we can
  54  * perform distance based culling. Distance based
  55  * culling doesn't require a face and can be performed
  56  * on primitives without faces (e.g. points and lines)
  57  */
  58 static void user_cull_point( struct draw_stage *stage,
  59                         struct prim_header *header )
  60 {
  61    const unsigned num_written_culldistances =
  62       draw_current_shader_num_written_culldistances(stage->draw);
  63    const unsigned num_written_clipdistances =
  64       draw_current_shader_num_written_clipdistances(stage->draw);
  65    unsigned i;
  66
  67    debug_assert(num_written_culldistances);
  68
  69    for (i = 0; i < num_written_culldistances; ++i) {
  70       unsigned cull_idx = (num_written_clipdistances + i) / 4;
  71       unsigned out_idx =
  72          draw_current_shader_ccdistance_output(stage->draw, cull_idx);
  73       unsigned idx = (num_written_clipdistances + i) % 4;
  74       float cull1 = header->v[0]->data[out_idx][idx];
  75       boolean vert1_out = cull_distance_is_out(cull1);
  76       if (vert1_out)
  77          return;
  78    }
  79    stage->next->point( stage->next, header );
  80 }
  81
  82 /*
  83  * If the shader writes the culldistance then we can
  84  * perform distance based culling. Distance based
  85  * culling doesn't require a face and can be performed
  86  * on primitives without faces (e.g. points and lines)
  87  */
  88 static void user_cull_line( struct draw_stage *stage,
  89                        struct prim_header *header )
  90 {
  91    const unsigned num_written_culldistances =
  92       draw_current_shader_num_written_culldistances(stage->draw);
  93    const unsigned num_written_clipdistances =
  94       draw_current_shader_num_written_clipdistances(stage->draw);
  95    unsigned i;
  96
  97    debug_assert(num_written_culldistances);
  98
  99    for (i = 0; i < num_written_culldistances; ++i) {
 100       unsigned cull_idx = (num_written_clipdistances + i) / 4;
 101       unsigned out_idx =
 102          draw_current_shader_ccdistance_output(stage->draw, cull_idx);
 103       unsigned idx = (num_written_clipdistances + i) % 4;
 104       float cull1 = header->v[0]->data[out_idx][idx];
 105       float cull2 = header->v[1]->data[out_idx][idx];
 106       boolean vert1_out = cull_distance_is_out(cull1);
 107       boolean vert2_out = cull_distance_is_out(cull2);
 108       if (vert1_out && vert2_out)
 109          return;
 110    }
 111    stage->next->line( stage->next, header );
 112 }
 113
 114 /*
 115  * Triangles can be culled either using the cull distance
 116  * shader outputs or the regular face culling. If required
 117  * this function performs both, starting with distance culling.
 118  */
 119 static void user_cull_tri( struct draw_stage *stage,
 120                            struct prim_header *header )
 121 {
 122    const unsigned num_written_culldistances =
 123       draw_current_shader_num_written_culldistances(stage->draw);
 124    const unsigned num_written_clipdistances =
 125       draw_current_shader_num_written_clipdistances(stage->draw);
 126    unsigned i;
 127
 128    debug_assert(num_written_culldistances);
 129
 130    /* Do the distance culling */
 131    for (i = 0; i < num_written_culldistances; ++i) {
 132       unsigned cull_idx = (num_written_clipdistances + i) / 4;
 133       unsigned out_idx =
 134          draw_current_shader_ccdistance_output(stage->draw, cull_idx);
 135       unsigned idx = (num_written_clipdistances + i) % 4;
 136       float cull1 = header->v[0]->data[out_idx][idx];
 137       float cull2 = header->v[1]->data[out_idx][idx];
 138       float cull3 = header->v[2]->data[out_idx][idx];
 139       boolean vert1_out = cull_distance_is_out(cull1);
 140       boolean vert2_out = cull_distance_is_out(cull2);
 141       boolean vert3_out = cull_distance_is_out(cull3);
 142       if (vert1_out && vert2_out && vert3_out) {
 143          return;
 144       }
 145    }
 146    stage->next->tri( stage->next, header );
 147 }
 148
 149 static void user_cull_flush( struct draw_stage *stage, unsigned flags )
 150 {
 151    stage->point = user_cull_point;
 152    stage->line = user_cull_line;
 153    stage->tri = user_cull_tri;
 154    stage->next->flush( stage->next, flags );
 155 }
 156
 157 static void user_cull_reset_stipple_counter( struct draw_stage *stage )
 158 {
 159    stage->next->reset_stipple_counter( stage->next );
 160 }
 161
 162 static void user_cull_destroy( struct draw_stage *stage )
 163 {
 164    draw_free_temp_verts( stage );
 165    FREE( stage );
 166 }
 167
 168 /**
 169  * Create a new polygon culling stage.
 170  */
 171 struct draw_stage *draw_user_cull_stage( struct draw_context *draw )
 172 {
 173    struct user_cull_stage *user_cull = CALLOC_STRUCT(user_cull_stage);
 174    if (!user_cull)
 175       goto fail;
 176
 177    user_cull->stage.draw = draw;
 178    user_cull->stage.name = "user_cull";
 179    user_cull->stage.next = NULL;
 180    user_cull->stage.point = user_cull_point;
 181    user_cull->stage.line = user_cull_line;
 182    user_cull->stage.tri = user_cull_tri;
 183    user_cull->stage.flush = user_cull_flush;
 184    user_cull->stage.reset_stipple_counter = user_cull_reset_stipple_counter;
 185    user_cull->stage.destroy = user_cull_destroy;
 186
 187    if (!draw_alloc_temp_verts( &user_cull->stage, 0 ))
 188       goto fail;
 189
 190    return &user_cull->stage;
 191
 192 fail:
 193    if (user_cull)
 194       user_cull->stage.destroy( &user_cull->stage );
 195
 196    return NULL;
 197 }