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    ushort pattern;
  52    ushort factor;
  53    bool smooth;
  54 };
  55
  56
  57 static inline struct stipple_stage *
  58 stipple_stage(struct draw_stage *stage)
  59 {
  60    return (struct stipple_stage *) stage;
  61 }
  62
  63
  64 /**
  65  * Compute interpolated vertex attributes for 'dst' at position 't'
  66  * between 'v0' and 'v1'.
  67  * XXX using linear interpolation for all attribs at this time.
  68  */
  69 static void
  70 screen_interp(struct draw_context *draw,
  71               struct vertex_header *dst,
  72               float t,
  73               const struct vertex_header *v0,
  74               const struct vertex_header *v1)
  75 {
  76    uint attr;
  77    uint num_outputs = draw_current_shader_outputs(draw);
  78    for (attr = 0; attr < num_outputs; attr++) {
  79       const float *val0 = v0->data[attr];
  80       const float *val1 = v1->data[attr];
  81       float *newv = dst->data[attr];
  82       uint i;
  83       for (i = 0; i < 4; i++) {
  84          newv[i] = val0[i] + t * (val1[i] - val0[i]);
  85       }
  86    }
  87 }
  88
  89
  90 static void
  91 emit_segment(struct draw_stage *stage, struct prim_header *header,
  92              float t0, float t1)
  93 {
  94    struct vertex_header *v0new = dup_vert(stage, header->v[0], 0);
  95    struct vertex_header *v1new = dup_vert(stage, header->v[1], 1);
  96    struct prim_header newprim = *header;
  97
  98    if (t0 > 0.0) {
  99       screen_interp(stage->draw, v0new, t0, header->v[0], header->v[1]);
 100       newprim.v[0] = v0new;
 101    }
 102
 103    if (t1 < 1.0) {
 104       screen_interp(stage->draw, v1new, t1, header->v[0], header->v[1]);
 105       newprim.v[1] = v1new;
 106    }
 107
 108    stage->next->line(stage->next, &newprim);
 109 }
 110
 111
 112 static inline bool
 113 stipple_test(int counter, ushort pattern, ushort factor)
 114 {
 115    int b = (counter / factor) & 0xf;
 116    return !!((1 << b) & pattern);
 117 }
 118
 119
 120 static void
 121 stipple_line(struct draw_stage *stage, struct prim_header *header)
 122 {
 123    struct stipple_stage *stipple = stipple_stage(stage);
 124    struct vertex_header *v0 = header->v[0];
 125    struct vertex_header *v1 = header->v[1];
 126    const unsigned pos = draw_current_shader_position_output(stage->draw);
 127    const float *pos0 = v0->data[pos];
 128    const float *pos1 = v1->data[pos];
 129    float start = 0;
 130    bool state = 0;
 131
 132    float x0 = pos0[0];
 133    float x1 = pos1[0];
 134    float y0 = pos0[1];
 135    float y1 = pos1[1];
 136
 137    float length;
 138    int i;
 139    int intlength;
 140
 141    if (header->flags & DRAW_PIPE_RESET_STIPPLE)
 142       stipple->counter = 0;
 143
 144    if (stipple->smooth) {
 145       float dx = x1 - x0;
 146       float dy = y1 - y0;
 147       length = sqrtf(dx*dx + dy*dy);
 148    } else {
 149       float dx = x0 > x1 ? x0 - x1 : x1 - x0;
 150       float dy = y0 > y1 ? y0 - y1 : y1 - y0;
 151       length = MAX2(dx, dy);
 152    }
 153
 154    if (util_is_inf_or_nan(length))
 155       intlength = 0;
 156    else
 157       intlength = ceilf(length);
 158
 159    /* XXX ToDo: instead of iterating pixel-by-pixel, use a look-up table.
 160     */
 161    for (i = 0; i < intlength; i++) {
 162       bool result = stipple_test((int)stipple->counter + i,
 163                                  stipple->pattern, stipple->factor);
 164       if (result != state) {
 165          /* changing from "off" to "on" or vice versa */
 166          if (state) {
 167             /* finishing an "on" segment */
 168             emit_segment(stage, header, start / length, i / length);
 169          }
 170          else {
 171             /* starting an "on" segment */
 172             start = (float)i;
 173          }
 174          state = result;
 175       }
 176    }
 177
 178    if (state && start < length)
 179       emit_segment(stage, header, start / length, 1.0);
 180
 181    stipple->counter += length;
 182 }
 183
 184
 185 static void
 186 reset_stipple_counter(struct draw_stage *stage)
 187 {
 188    struct stipple_stage *stipple = stipple_stage(stage);
 189    stipple->counter = 0;
 190    stage->next->reset_stipple_counter(stage->next);
 191 }
 192
 193 static void
 194 stipple_reset_point(struct draw_stage *stage, struct prim_header *header)
 195 {
 196    struct stipple_stage *stipple = stipple_stage(stage);
 197    stipple->counter = 0;
 198    stage->next->point(stage->next, header);
 199 }
 200
 201 static void
 202 stipple_reset_tri(struct draw_stage *stage, struct prim_header *header)
 203 {
 204    struct stipple_stage *stipple = stipple_stage(stage);
 205    stipple->counter = 0;
 206    stage->next->tri(stage->next, header);
 207 }
 208
 209
 210 static void
 211 stipple_first_line(struct draw_stage *stage,
 212                    struct prim_header *header)
 213 {
 214    struct stipple_stage *stipple = stipple_stage(stage);
 215    struct draw_context *draw = stage->draw;
 216
 217    stipple->pattern = draw->rasterizer->line_stipple_pattern;
 218    stipple->factor = draw->rasterizer->line_stipple_factor + 1;
 219    stipple->smooth = draw->rasterizer->line_smooth;
 220
 221    stage->line = stipple_line;
 222    stage->line(stage, header);
 223 }
 224
 225
 226 static void
 227 stipple_flush(struct draw_stage *stage, unsigned flags)
 228 {
 229    stage->line = stipple_first_line;
 230    stage->next->flush(stage->next, flags);
 231 }
 232
 233
 234 static void
 235 stipple_destroy(struct draw_stage *stage)
 236 {
 237    draw_free_temp_verts(stage);
 238    FREE(stage);
 239 }
 240
 241
 242 /**
 243  * Create line stippler stage
 244  */
 245 struct draw_stage *
 246 draw_stipple_stage(struct draw_context *draw)
 247 {
 248    struct stipple_stage *stipple = CALLOC_STRUCT(stipple_stage);
 249    if (!stipple)
 250       goto fail;
 251
 252    stipple->stage.draw = draw;
 253    stipple->stage.name = "stipple";
 254    stipple->stage.next = NULL;
 255    stipple->stage.point = stipple_reset_point;
 256    stipple->stage.line = stipple_first_line;
 257    stipple->stage.tri = stipple_reset_tri;
 258    stipple->stage.reset_stipple_counter = reset_stipple_counter;
 259    stipple->stage.flush = stipple_flush;
 260    stipple->stage.destroy = stipple_destroy;
 261
 262    if (!draw_alloc_temp_verts(&stipple->stage, 2))
 263       goto fail;
 264
 265    return &stipple->stage;
 266
 267 fail:
 268    if (stipple)
 269       stipple->stage.destroy(&stipple->stage);
 270
 271    return NULL;
 272 }