src/gallium/auxiliary/draw/draw_pipe_stipple.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
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  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
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  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
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  26  **************************************************************************/
  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_pipe.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  * XXX using linear interpolation for all attribs at this time.
  65  */
  66 static void
  67 screen_interp( struct draw_context *draw,
  68                struct vertex_header *dst,
  69                float t,
  70                const struct vertex_header *v0,
  71                const struct vertex_header *v1 )
  72 {
  73    uint attr;
  74    for (attr = 0; attr < draw->num_vs_outputs; attr++) {
  75       const float *val0 = v0->data[attr];
  76       const float *val1 = v1->data[attr];
  77       float *newv = dst->data[attr];
  78       uint i;
  79       for (i = 0; i < 4; i++) {
  80          newv[i] = val0[i] + t * (val1[i] - val0[i]);
  81       }
  82    }
  83 }
  84
  85
  86 static void
  87 emit_segment(struct draw_stage *stage, struct prim_header *header,
  88              float t0, float t1)
  89 {
  90    struct vertex_header *v0new = dup_vert(stage, header->v[0], 0);
  91    struct vertex_header *v1new = dup_vert(stage, header->v[1], 1);
  92    struct prim_header newprim = *header;
  93
  94    if (t0 > 0.0) {
  95       screen_interp( stage->draw, v0new, t0, header->v[0], header->v[1] );
  96       newprim.v[0] = v0new;
  97    }
  98
  99    if (t1 < 1.0) {
 100       screen_interp( stage->draw, v1new, t1, header->v[0], header->v[1] );
 101       newprim.v[1] = v1new;
 102    }
 103
 104    stage->next->line( stage->next, &newprim );
 105 }
 106
 107
 108 static INLINE unsigned
 109 stipple_test(int counter, ushort pattern, int factor)
 110 {
 111    int b = (counter / factor) & 0xf;
 112    return (1 << b) & pattern;
 113 }
 114
 115
 116 static void
 117 stipple_line(struct draw_stage *stage, struct prim_header *header)
 118 {
 119    struct stipple_stage *stipple = stipple_stage(stage);
 120    struct vertex_header *v0 = header->v[0];
 121    struct vertex_header *v1 = header->v[1];
 122    const float *pos0 = v0->data[0];
 123    const float *pos1 = v1->data[0];
 124    float start = 0;
 125    int state = 0;
 126
 127    float x0 = pos0[0];
 128    float x1 = pos1[0];
 129    float y0 = pos0[1];
 130    float y1 = pos1[1];
 131
 132    float dx = x0 > x1 ? x0 - x1 : x1 - x0;
 133    float dy = y0 > y1 ? y0 - y1 : y1 - y0;
 134
 135    float length = MAX2(dx, dy);
 136    int i;
 137
 138    if (header->flags & DRAW_PIPE_RESET_STIPPLE)
 139       stipple->counter = 0;
 140
 141
 142    /* XXX ToDo: intead of iterating pixel-by-pixel, use a look-up table.
 143     */
 144    for (i = 0; i < length; i++) {
 145       int result = stipple_test( (int) stipple->counter+i,
 146                                  (ushort) stipple->pattern, stipple->factor );
 147       if (result != state) {
 148          /* changing from "off" to "on" or vice versa */
 149          if (state) {
 150             if (start != i) {
 151                /* finishing an "on" segment */
 152                emit_segment( stage, header, start / length, i / length );
 153             }
 154          }
 155          else {
 156             /* starting an "on" segment */
 157             start = (float) i;
 158          }
 159          state = result;
 160       }
 161    }
 162
 163    if (state && start < length)
 164       emit_segment( stage, header, start / length, 1.0 );
 165
 166    stipple->counter += length;
 167 }
 168
 169
 170 static void
 171 reset_stipple_counter(struct draw_stage *stage)
 172 {
 173    struct stipple_stage *stipple = stipple_stage(stage);
 174    stipple->counter = 0;
 175    stage->next->reset_stipple_counter( stage->next );
 176 }
 177
 178
 179 static void
 180 stipple_first_line(struct draw_stage *stage,
 181                    struct prim_header *header)
 182 {
 183    struct stipple_stage *stipple = stipple_stage(stage);
 184    struct draw_context *draw = stage->draw;
 185
 186    stipple->pattern = draw->rasterizer->line_stipple_pattern;
 187    stipple->factor = draw->rasterizer->line_stipple_factor + 1;
 188
 189    stage->line = stipple_line;
 190    stage->line( stage, header );
 191 }
 192
 193
 194 static void
 195 stipple_flush(struct draw_stage *stage, unsigned flags)
 196 {
 197    stage->line = stipple_first_line;
 198    stage->next->flush( stage->next, flags );
 199 }
 200
 201
 202
 203
 204 static void
 205 stipple_destroy( struct draw_stage *stage )
 206 {
 207    draw_free_temp_verts( stage );
 208    FREE( stage );
 209 }
 210
 211
 212 /**
 213  * Create line stippler stage
 214  */
 215 struct draw_stage *draw_stipple_stage( struct draw_context *draw )
 216 {
 217    struct stipple_stage *stipple = CALLOC_STRUCT(stipple_stage);
 218
 219    draw_alloc_temp_verts( &stipple->stage, 2 );
 220
 221    stipple->stage.draw = draw;
 222    stipple->stage.next = NULL;
 223    stipple->stage.point = draw_pipe_passthrough_point;
 224    stipple->stage.line = stipple_first_line;
 225    stipple->stage.tri = draw_pipe_passthrough_tri;
 226    stipple->stage.reset_stipple_counter = reset_stipple_counter;
 227    stipple->stage.flush = stipple_flush;
 228    stipple->stage.destroy = stipple_destroy;
 229
 230    return &stipple->stage;
 231 }