src/gallium/auxiliary/draw/draw_pipe_stipple.c

   1 /**************************************************************************
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   3  * Copyright 2007 VMware, Inc.
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  27
  28 /* Authors:  Keith Whitwell <keithw@vmware.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_defines.h"
  40 #include "pipe/p_shader_tokens.h"
  41 #include "util/u_math.h"
  42 #include "util/u_memory.h"
  43
  44 #include "draw/draw_pipe.h"
  45
  46
  47 /** Subclass of draw_stage */
  48 struct stipple_stage {
  49    struct draw_stage stage;
  50    float counter;
  51    uint pattern;
  52    uint factor;
  53 };
  54
  55
  56 static INLINE struct stipple_stage *
  57 stipple_stage(struct draw_stage *stage)
  58 {
  59    return (struct stipple_stage *) stage;
  60 }
  61
  62
  63 /**
  64  * Compute interpolated vertex attributes for 'dst' at position 't'
  65  * between 'v0' and 'v1'.
  66  * XXX using linear interpolation for all attribs at this time.
  67  */
  68 static void
  69 screen_interp( struct draw_context *draw,
  70                struct vertex_header *dst,
  71                float t,
  72                const struct vertex_header *v0,
  73                const struct vertex_header *v1 )
  74 {
  75    uint attr;
  76    uint num_outputs = draw_current_shader_outputs(draw);
  77    for (attr = 0; attr < num_outputs; attr++) {
  78       const float *val0 = v0->data[attr];
  79       const float *val1 = v1->data[attr];
  80       float *newv = dst->data[attr];
  81       uint i;
  82       for (i = 0; i < 4; i++) {
  83          newv[i] = val0[i] + t * (val1[i] - val0[i]);
  84       }
  85    }
  86 }
  87
  88
  89 static void
  90 emit_segment(struct draw_stage *stage, struct prim_header *header,
  91              float t0, float t1)
  92 {
  93    struct vertex_header *v0new = dup_vert(stage, header->v[0], 0);
  94    struct vertex_header *v1new = dup_vert(stage, header->v[1], 1);
  95    struct prim_header newprim = *header;
  96
  97    if (t0 > 0.0) {
  98       screen_interp( stage->draw, v0new, t0, header->v[0], header->v[1] );
  99       newprim.v[0] = v0new;
 100    }
 101
 102    if (t1 < 1.0) {
 103       screen_interp( stage->draw, v1new, t1, header->v[0], header->v[1] );
 104       newprim.v[1] = v1new;
 105    }
 106
 107    stage->next->line( stage->next, &newprim );
 108 }
 109
 110
 111 static INLINE unsigned
 112 stipple_test(int counter, ushort pattern, int factor)
 113 {
 114    int b = (counter / factor) & 0xf;
 115    return (1 << b) & pattern;
 116 }
 117
 118
 119 static void
 120 stipple_line(struct draw_stage *stage, struct prim_header *header)
 121 {
 122    struct stipple_stage *stipple = stipple_stage(stage);
 123    struct vertex_header *v0 = header->v[0];
 124    struct vertex_header *v1 = header->v[1];
 125    const unsigned pos = draw_current_shader_position_output(stage->draw);
 126    const float *pos0 = v0->data[pos];
 127    const float *pos1 = v1->data[pos];
 128    float start = 0;
 129    int state = 0;
 130
 131    float x0 = pos0[0];
 132    float x1 = pos1[0];
 133    float y0 = pos0[1];
 134    float y1 = pos1[1];
 135
 136    float dx = x0 > x1 ? x0 - x1 : x1 - x0;
 137    float dy = y0 > y1 ? y0 - y1 : y1 - y0;
 138
 139    float length = MAX2(dx, dy);
 140    int i;
 141
 142    if (header->flags & DRAW_PIPE_RESET_STIPPLE)
 143       stipple->counter = 0;
 144
 145
 146    /* XXX ToDo: intead of iterating pixel-by-pixel, use a look-up table.
 147     */
 148    for (i = 0; i < length; i++) {
 149       int result = stipple_test( (int) stipple->counter+i,
 150                                  (ushort) stipple->pattern, stipple->factor );
 151       if (result != state) {
 152          /* changing from "off" to "on" or vice versa */
 153          if (state) {
 154             if (start != i) {
 155                /* finishing an "on" segment */
 156                emit_segment( stage, header, start / length, i / length );
 157             }
 158          }
 159          else {
 160             /* starting an "on" segment */
 161             start = (float) i;
 162          }
 163          state = result;
 164       }
 165    }
 166
 167    if (state && start < length)
 168       emit_segment( stage, header, start / length, 1.0 );
 169
 170    stipple->counter += length;
 171 }
 172
 173
 174 static void
 175 reset_stipple_counter(struct draw_stage *stage)
 176 {
 177    struct stipple_stage *stipple = stipple_stage(stage);
 178    stipple->counter = 0;
 179    stage->next->reset_stipple_counter( stage->next );
 180 }
 181
 182 static void
 183 stipple_reset_point(struct draw_stage *stage, struct prim_header *header)
 184 {
 185    struct stipple_stage *stipple = stipple_stage(stage);
 186    stipple->counter = 0;
 187    stage->next->point(stage->next, header);
 188 }
 189
 190 static void
 191 stipple_reset_tri(struct draw_stage *stage, struct prim_header *header)
 192 {
 193    struct stipple_stage *stipple = stipple_stage(stage);
 194    stipple->counter = 0;
 195    stage->next->tri(stage->next, header);
 196 }
 197
 198
 199 static void
 200 stipple_first_line(struct draw_stage *stage,
 201                    struct prim_header *header)
 202 {
 203    struct stipple_stage *stipple = stipple_stage(stage);
 204    struct draw_context *draw = stage->draw;
 205
 206    stipple->pattern = draw->rasterizer->line_stipple_pattern;
 207    stipple->factor = draw->rasterizer->line_stipple_factor + 1;
 208
 209    stage->line = stipple_line;
 210    stage->line( stage, header );
 211 }
 212
 213
 214 static void
 215 stipple_flush(struct draw_stage *stage, unsigned flags)
 216 {
 217    stage->line = stipple_first_line;
 218    stage->next->flush( stage->next, flags );
 219 }
 220
 221
 222
 223
 224 static void
 225 stipple_destroy( struct draw_stage *stage )
 226 {
 227    draw_free_temp_verts( stage );
 228    FREE( stage );
 229 }
 230
 231
 232 /**
 233  * Create line stippler stage
 234  */
 235 struct draw_stage *draw_stipple_stage( struct draw_context *draw )
 236 {
 237    struct stipple_stage *stipple = CALLOC_STRUCT(stipple_stage);
 238    if (stipple == NULL)
 239       goto fail;
 240
 241    stipple->stage.draw = draw;
 242    stipple->stage.name = "stipple";
 243    stipple->stage.next = NULL;
 244    stipple->stage.point = stipple_reset_point;
 245    stipple->stage.line = stipple_first_line;
 246    stipple->stage.tri = stipple_reset_tri;
 247    stipple->stage.reset_stipple_counter = reset_stipple_counter;
 248    stipple->stage.flush = stipple_flush;
 249    stipple->stage.destroy = stipple_destroy;
 250
 251    if (!draw_alloc_temp_verts( &stipple->stage, 2 ))
 252       goto fail;
 253
 254    return &stipple->stage;
 255
 256 fail:
 257    if (stipple)
 258       stipple->stage.destroy( &stipple->stage );
 259
 260    return NULL;
 261 }