src/mesa/pipe/draw/draw_stipple.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
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  11  * permit persons to whom the Software is furnished to do so, subject to
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  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
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  27
  28 /* Authors:  Keith Whitwell <keith@tungstengraphics.com>
  29  */
  30
  31 /* Implement line stipple by cutting lines up into smaller lines.
  32  * There are hundreds of ways to implement line stipple, this is one
  33  * choice that should work in all situations, requires no state
  34  * manipulations, but with a penalty in terms of large amounts of
  35  * generated geometry.
  36  */
  37
  38
  39 #include "pipe/p_util.h"
  40 #include "pipe/p_defines.h"
  41 #include "pipe/p_shader_tokens.h"
  42 #include "draw_private.h"
  43
  44
  45 /** Subclass of draw_stage */
  46 struct stipple_stage {
  47    struct draw_stage stage;
  48    float counter;
  49    uint pattern;
  50    uint factor;
  51 };
  52
  53
  54 static INLINE struct stipple_stage *
  55 stipple_stage(struct draw_stage *stage)
  56 {
  57    return (struct stipple_stage *) stage;
  58 }
  59
  60
  61 /**
  62  * Compute interpolated vertex attributes for 'dst' at position 't'
  63  * between 'v0' and 'v1'.
  64  */
  65 static void
  66 screen_interp( struct draw_context *draw,
  67                struct vertex_header *dst,
  68                float t,
  69                const struct vertex_header *v0,
  70                const struct vertex_header *v1 )
  71 {
  72    uint attr;
  73    for (attr = 0; attr < draw->vertex_info.num_attribs; attr++) {
  74       switch (draw->vertex_info.interp_mode[attr]) {
  75       case INTERP_NONE:
  76       case INTERP_CONSTANT:
  77          COPY_4FV(dst->data[attr], v0->data[attr]);
  78          break;
  79       case INTERP_PERSPECTIVE:
  80          /* Fall-through */
  81          /* XXX special-case perspective? */
  82       case INTERP_LINEAR:
  83          {
  84             const float *val0 = v0->data[attr];
  85             const float *val1 = v1->data[attr];
  86             float *newv = dst->data[attr];
  87             uint i;
  88             for (i = 0; i < 4; i++) {
  89                newv[i] = val0[i] + t * (val1[i] - val0[i]);
  90             }
  91          }
  92          break;
  93       default:
  94          abort();
  95       }
  96    }
  97 }
  98
  99
 100 static void
 101 emit_segment(struct draw_stage *stage, struct prim_header *header,
 102              float t0, float t1)
 103 {
 104    struct vertex_header *v0new = dup_vert(stage, header->v[0], 0);
 105    struct vertex_header *v1new = dup_vert(stage, header->v[1], 1);
 106    struct prim_header newprim = *header;
 107
 108    if (t0 > 0.0) {
 109       screen_interp( stage->draw, v0new, t0, header->v[0], header->v[1] );
 110       newprim.v[0] = v0new;
 111    }
 112
 113    if (t1 < 1.0) {
 114       screen_interp( stage->draw, v1new, t1, header->v[0], header->v[1] );
 115       newprim.v[1] = v1new;
 116    }
 117
 118    stage->next->line( stage->next, &newprim );
 119 }
 120
 121
 122 static INLINE unsigned
 123 stipple_test(int counter, ushort pattern, int factor)
 124 {
 125    int b = (counter / factor) & 0xf;
 126    return (1 << b) & pattern;
 127 }
 128
 129
 130 static void
 131 stipple_line(struct draw_stage *stage, struct prim_header *header)
 132 {
 133    struct stipple_stage *stipple = stipple_stage(stage);
 134    struct vertex_header *v0 = header->v[0];
 135    struct vertex_header *v1 = header->v[1];
 136    const float *pos0 = v0->data[0];
 137    const float *pos1 = v1->data[0];
 138    float start = 0;
 139    int state = 0;
 140
 141    float x0 = pos0[0];
 142    float x1 = pos1[0];
 143    float y0 = pos0[1];
 144    float y1 = pos1[1];
 145
 146    float dx = x0 > x1 ? x0 - x1 : x1 - x0;
 147    float dy = y0 > y1 ? y0 - y1 : y1 - y0;
 148
 149    float length = MAX2(dx, dy);
 150    int i;
 151
 152    /* XXX ToDo: intead of iterating pixel-by-pixel, use a look-up table.
 153     */
 154    for (i = 0; i < length; i++) {
 155       int result = stipple_test( (int) stipple->counter+i,
 156                                  (ushort) stipple->pattern, stipple->factor );
 157       if (result != state) {
 158          /* changing from "off" to "on" or vice versa */
 159          if (state) {
 160             if (start != i) {
 161                /* finishing an "on" segment */
 162                emit_segment( stage, header, start / length, i / length );
 163             }
 164          }
 165          else {
 166             /* starting an "on" segment */
 167             start = (float) i;
 168          }
 169          state = result;
 170       }
 171    }
 172
 173    if (state && start < length)
 174       emit_segment( stage, header, start / length, 1.0 );
 175
 176    stipple->counter += length;
 177 }
 178
 179
 180 static void
 181 reset_stipple_counter(struct draw_stage *stage)
 182 {
 183    struct stipple_stage *stipple = stipple_stage(stage);
 184    stipple->counter = 0;
 185    stage->next->reset_stipple_counter( stage->next );
 186 }
 187
 188
 189 static void
 190 stipple_begin(struct draw_stage *stage)
 191 {
 192    struct stipple_stage *stipple = stipple_stage(stage);
 193    struct draw_context *draw = stage->draw;
 194
 195    stipple->pattern = draw->rasterizer->line_stipple_pattern;
 196    stipple->factor = draw->rasterizer->line_stipple_factor + 1;
 197
 198    stage->next->begin( stage->next );
 199 }
 200
 201
 202 static void
 203 stipple_end(struct draw_stage *stage)
 204 {
 205    stage->next->end( stage->next );
 206 }
 207
 208
 209 static void
 210 passthrough_point(struct draw_stage *stage, struct prim_header *header)
 211 {
 212    stage->next->point( stage->next, header );
 213 }
 214
 215
 216 static void
 217 passthrough_tri(struct draw_stage *stage, struct prim_header *header)
 218 {
 219    stage->next->tri(stage->next, header);
 220 }
 221
 222
 223 static void
 224 stipple_destroy( struct draw_stage *stage )
 225 {
 226    FREE( stage );
 227 }
 228
 229
 230 /**
 231  * Create line stippler stage
 232  */
 233 struct draw_stage *draw_stipple_stage( struct draw_context *draw )
 234 {
 235    struct stipple_stage *stipple = CALLOC_STRUCT(stipple_stage);
 236
 237    draw_alloc_tmps( &stipple->stage, 2 );
 238
 239    stipple->stage.draw = draw;
 240    stipple->stage.next = NULL;
 241    stipple->stage.begin = stipple_begin;
 242    stipple->stage.point = passthrough_point;
 243    stipple->stage.line = stipple_line;
 244    stipple->stage.tri = passthrough_tri;
 245    stipple->stage.reset_stipple_counter = reset_stipple_counter;
 246    stipple->stage.end = stipple_end;
 247    stipple->stage.destroy = stipple_destroy;
 248
 249    return &stipple->stage;
 250 }