src/gallium/auxiliary/draw/draw_pipe_wide_line.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  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
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28 /* Authors:  Keith Whitwell <keith@tungstengraphics.com>
  29  */
  30
  31 #include "pipe/p_defines.h"
  32 #include "pipe/p_shader_tokens.h"
  33 #include "util/u_math.h"
  34 #include "util/u_memory.h"
  35 #include "draw_private.h"
  36 #include "draw_pipe.h"
  37
  38
  39 struct wideline_stage {
  40    struct draw_stage stage;
  41
  42    float half_line_width;
  43 };
  44
  45
  46
  47 static INLINE struct wideline_stage *wideline_stage( struct draw_stage *stage )
  48 {
  49    return (struct wideline_stage *)stage;
  50 }
  51
  52
  53
  54 /**
  55  * Draw a wide line by drawing a quad (two triangles).
  56  * XXX need to disable polygon stipple.
  57  */
  58 static void wideline_line( struct draw_stage *stage,
  59                            struct prim_header *header )
  60 {
  61    /*const struct wideline_stage *wide = wideline_stage(stage);*/
  62    const unsigned pos = stage->draw->vs.position_output;
  63    const float half_width = 0.5f * stage->draw->rasterizer->line_width;
  64
  65    struct prim_header tri;
  66
  67    struct vertex_header *v0 = dup_vert(stage, header->v[0], 0);
  68    struct vertex_header *v1 = dup_vert(stage, header->v[0], 1);
  69    struct vertex_header *v2 = dup_vert(stage, header->v[1], 2);
  70    struct vertex_header *v3 = dup_vert(stage, header->v[1], 3);
  71
  72    float *pos0 = v0->data[pos];
  73    float *pos1 = v1->data[pos];
  74    float *pos2 = v2->data[pos];
  75    float *pos3 = v3->data[pos];
  76
  77    const float dx = fabsf(pos0[0] - pos2[0]);
  78    const float dy = fabsf(pos0[1] - pos2[1]);
  79
  80    /* small tweak to meet GL specification */
  81    const float bias = 0.125f;
  82
  83    /*
  84     * Draw wide line as a quad (two tris) by "stretching" the line along
  85     * X or Y.
  86     * We need to tweak coords in several ways to be conformant here.
  87     */
  88
  89    if (dx > dy) {
  90       /* x-major line */
  91       pos0[1] = pos0[1] - half_width - bias;
  92       pos1[1] = pos1[1] + half_width - bias;
  93       pos2[1] = pos2[1] - half_width - bias;
  94       pos3[1] = pos3[1] + half_width - bias;
  95       if (pos0[0] < pos2[0]) {
  96          /* left to right line */
  97          pos0[0] -= 0.5f;
  98          pos1[0] -= 0.5f;
  99          pos2[0] -= 0.5f;
 100          pos3[0] -= 0.5f;
 101       }
 102       else {
 103          /* right to left line */
 104          pos0[0] += 0.5f;
 105          pos1[0] += 0.5f;
 106          pos2[0] += 0.5f;
 107          pos3[0] += 0.5f;
 108       }
 109    }
 110    else {
 111       /* y-major line */
 112       pos0[0] = pos0[0] - half_width + bias;
 113       pos1[0] = pos1[0] + half_width + bias;
 114       pos2[0] = pos2[0] - half_width + bias;
 115       pos3[0] = pos3[0] + half_width + bias;
 116       if (pos0[1] < pos2[1]) {
 117          /* top to bottom line */
 118          pos0[1] -= 0.5f;
 119          pos1[1] -= 0.5f;
 120          pos2[1] -= 0.5f;
 121          pos3[1] -= 0.5f;
 122       }
 123       else {
 124          /* bottom to top line */
 125          pos0[1] += 0.5f;
 126          pos1[1] += 0.5f;
 127          pos2[1] += 0.5f;
 128          pos3[1] += 0.5f;
 129       }
 130    }
 131
 132    tri.det = header->det;  /* only the sign matters */
 133    tri.v[0] = v0;
 134    tri.v[1] = v2;
 135    tri.v[2] = v3;
 136    stage->next->tri( stage->next, &tri );
 137
 138    tri.v[0] = v0;
 139    tri.v[1] = v3;
 140    tri.v[2] = v1;
 141    stage->next->tri( stage->next, &tri );
 142 }
 143
 144
 145 static void wideline_flush( struct draw_stage *stage, unsigned flags )
 146 {
 147    stage->next->flush( stage->next, flags );
 148 }
 149
 150
 151 static void wideline_reset_stipple_counter( struct draw_stage *stage )
 152 {
 153    stage->next->reset_stipple_counter( stage->next );
 154 }
 155
 156
 157 static void wideline_destroy( struct draw_stage *stage )
 158 {
 159    draw_free_temp_verts( stage );
 160    FREE( stage );
 161 }
 162
 163
 164 struct draw_stage *draw_wide_line_stage( struct draw_context *draw )
 165 {
 166    struct wideline_stage *wide = CALLOC_STRUCT(wideline_stage);
 167
 168    draw_alloc_temp_verts( &wide->stage, 4 );
 169
 170    wide->stage.draw = draw;
 171    wide->stage.next = NULL;
 172    wide->stage.point = draw_pipe_passthrough_point;
 173    wide->stage.line = wideline_line;
 174    wide->stage.tri = draw_pipe_passthrough_tri;
 175    wide->stage.flush = wideline_flush;
 176    wide->stage.reset_stipple_counter = wideline_reset_stipple_counter;
 177    wide->stage.destroy = wideline_destroy;
 178
 179    return &wide->stage;
 180 }